And that concludes our coverage for this evening, we will be resuming on Thursday morning.
You can still follow the latest updates via the main news story.
As EU interior and justice ministers prepare for Thursday's talks in Brussels to discuss how to deal with jihadist attacks in Europe, the BBC's Katya Adler in the Belgian capital predicts that the meeting will not be an easy one.
Taking into account a forthcoming referendum in Britain on EU membership and recent strident nationalistic statements by some EU members, our correspondent says the idea of a more unified European response to the jihadist threat is "not going to be very digestible" for some European governments.
BBC's Anna Holligan in Brussels tweets:
Nicolas Henin, the French journalist who was for months held hostage by the so-called Islamic State in Syria, writes in the Guardian newspaper that while the Brussels attacks had a lower death toll than those in Paris last November, they have a different significance.
The Brussels attack marks the migration of terror from one country to the next. Suddenly everyone is saying: who is the terrorist, and where will they strike next – the UK? Germany? The Netherlands?
But while Khalid and Brahim el-Bakraoui and, reports say, Najim Laachraoui performed their duty to die as "cannon fodder" for IS, Mr Henin says that the unwillingness to kill himself of another militant - Salah Abdeslam, who has been arrested - represents an opportunity.
First in Paris and now in Brussels, he has twice refused to meet his death. Perhaps there are signs of hope in this, for it shows that if there is a weakness in Isis, it is that there are humans in its ranks
Mr Henin says how Europe reacts now will be crucial - but, he says, the omens are not good. Already French President Francois Hollande has, he says, "fallen into the trap" of referring to this challenge as a war.
We have seen large-scale political violence before in our history. If we adopt a militaristic, warlike vocabulary, there will be no way back from that. We will only strengthen our enemies
RTBF is now also reporting that the Rue de la Loi street and two tunnels closed after Tuesday's attacks have now re-opened.
Earlier, a group of Belgian Muslims brought a message of peace to the centre of Brussels.
Belgium's RTBF public broadcaster has reported that Brussels' metro system will be operating from 07:00 local time (08:00 GMT) to 19:00 only, and access to train stations will be limited.
When Belgian police raided an apartment in the Schaerbeek area of Brussels, linked to the attackers, they found bomb-making materials, including 15kg (33lb) of TATP.
This powerful DIY explosive was also used by terrorists in Paris and in the 2007 London bombings.
Details are continuing to emerge about what happened yesterday, including the identities of the suicide bombers. A manhunt is still underway for a third airport attacker, so far unnamed, whose device failed to detonate.
Here is a comprehensive round up what we know so far - and the suspected links between the Brussels and Paris terror attacks.
Daniel Byman, an extremism expert at Georgetown University and the Brookings Institution, writes in the New York Times that while the group Islamic State (IS) may be on the defensive in Iraq and Syria, it is lashing out abroad and Europe is emerging as a "key battleground".
Mr Byman says that returnees from Syria and Iraq are linking up with locals, creating a "self-sustaining cycle of violence".
The first volunteers were motivated primarily by adventure or out of a sense of defending their community, but now friends are recruiting friends, promising glory and God
Across the Continent, Muslims often feel alienated from the broader population. In the US, many plots are disrupted because the American Muslim community reports them to the police and the FBI; such trust is lacking in Europe
The rise of far-right, xenophobic political forces, like the National Front in France or Alternative for Germany, will do little to improve relations between European Muslims and their governments
Unfortunately, the Western response in Iraq and Syria is much more promising than efforts to stop terrorism in Europe
Journalist Kate Kardava was in Brussels airport at the time of the blasts. Photographs she took of the aftermath with her mobile phone have appeared in newspapers all over the world. She tells the BBC about her experience.
An IT programmer from Nottingham - David Dixon - has been missing since the terror attacks in Brussels. Family friend Simon Hartley-Jones told the BBC that his partner Charlotte Sutcliffe has been searching the city's hospitals for him. Mr Hartley-Jones describes his friend as an "amazing man who deeply, deeply loves his son".
From BBC Monitoring:
Belgium's RTBF correspondent reporting from Brussels' Place de la Bourse - where a large crowd has gathered to pay tribute to the victims of the attacks - says the square "has taken on the appearance of the Place de la Republique in Paris in the aftermath of the Charlie Hebdo and 13 November attacks".
People have been tweeting their tributes to those caught up in the Brussels attacks:
On Wednesday night, employees of Brussels' Zaventem airport took part in a "silent walk" to pay tributes to the victims of the attacks.
In its special live coverage of the aftermath of the Brussels attacks, Belgian public service broadcaster RTBF continues to alternate between news updates, studio discussions with security experts and footage showing the crowds gathered in the Place de la Bourse in Brussels to pay tribute to the victims of the attacks.
Many people lit candles as darkness fell, and Moroccan, Tunisian, Turkish and other flags from all over the world were shown displayed alongside the Belgian flag.
One woman told the RTBF interviewer that she had come with her family in order to express her solidarity and "to find again the former Belgium". Asked what this Belgium meant to her, she said it was a country "in which people used to smile at each other and talk to each other".
A provisional update sent by the office of Belgian Health Minister Maggie De Block says 31 people are dead and 300 injured, of which 150 remain in hospital.
Brussels airport officials are now saying the earliest resumption of flights could be on Saturday.
The Bakraoui brothers were the latest in a series of siblings to have been involved in terror cells, says Belgian newspaper L'Echo.
They follow the Abdeslam brothers who were involved in the Paris attacks last November, the Kouachi brothers who carried out the Charlie Hebdo attacks in January 2015, the Tsarnaev brothers who bombed the Boston marathon in 2013 and Abdelkader Merah, who was charged with helping his brother Mohammed carry out a deadly gun rampage in Toulouse in 2012. The 9/11 attackers also counted sets of brothers among their number.
Former CIA agent Marc Sageman tells L'Echo that it is a "natural phenomenon".
They grow up together, they grumble and invent an identity as defenders of an Islam that is under threat, of women and children killed in air strikes. They radicalise and validate one another
When you need someone to go along with you, the most logical target is your younger or older brother. It's the same with street gangs. There is no need for brainwashing or indoctrination
Psychoanalyst Patrick Amoyel from Nice has worked to deradicalise young people in France.
They wrap themselves up in a kind of psychological confusion. There is something a little crazy and irrational in these processes. An adolescent form of risk-taking, even if they are no longer adolescents
Mr Amoyel says this "bubble of radicalisation" can grow to include others, for example a best friend who marries the brothers' sister.
At this level there is a consolidation that is very hard to break. I have seen it very often. And it has nothing to do with mental illness, it is not something psychotic or psycho-pathological
It goes round and round, one influences the others and vice versa and it can spin out of control. There can be a desire to go beyond the limits towards absolute rebellion. And that can lead to terrorist action
The Belgian authorities are continuing to identify the victims of the bombings. Meanwhile, families and friends are desperately searching for people missing since yesterday's attacks.
French newspaper Le Monde and several Belgian news outlets have identified the second suicide bomber at Zaventem Airport as Najim Laachraoui.
Laachraoui was named earlier in the week by police as a wanted accomplice of Salah Abdeslam.
Analysts say Laachraoui is believed to be a key bomb maker, and French media say he also played a major role in the terror attacks in Paris.
A neighbour of the El Bakraoui brothers saw two people carrying heavy bags early on the morning of the attacks, news agency AP reports.
Erdine, 36, who declined to give his last name due to the situation, said he was about to drive his son to school around 07:30 local time when the two people and a cab driver open his trunk.
He said: "The taxi driver tried to get the luggage. And the other guy reached for it like he was saying, 'No, I'll take it'."
Prosecutors say a taxi driver tipped them off to the address in the Schaerbeek neighbourhood of Brussels after the attacks.
Meanwhile, other neighbours expressed shock and bewilderment at what happened.
John Valderrama, who lived across the hall from Khalid and Brahim el-Bakraoui, told AP he never heard anything suspicious.
He said he only saw one person come in or out of the fifth-floor apartment. He was surprised when hours after yesterday's attack, police burst into the brothers' apartment. Police discovered a large cache of TATP explosives there.
The Turkish presidency has identified the Brussels attacker deported by Turkey last July as Brahim El Bakraoui, who blew himself up at Zaventem Airport.
It follows Turkish President Erdogan's assertion that Turkey had deported one of the Brussels attackers and warned the Belgian authorities he was a militant.
Mr Erdogan said the man was detained at Turkey's border with Syria at Gaziantep
The Turkish presidency said El Bakraoui was later released by the Belgian authorities because they had found "no links with terrorism".
There are still dozens of passengers being escorted out of the Brussels airport security zone, a day on from the biggest terrorist atrocity to hit Belgium. They were guests at the Sheraton Airport hotel.
Security services had advised spending the night at the hotel for their own safety, and intelligence officers have been visiting each room, interviewing guests and looking for anything suspicious. The hotel foyer became the immediate triage area for medical teams, bringing in the casualties and the bodies of those who died.
Now, dozens of military police and soldiers guard the airport entrance, with access only for forensic teams, investigators and airport staff. Several ‘ghost flights’ with no passengers on board set off this afternoon. Airlines are starting to move their aircrafts elsewhere, aware that "business as usual" at Brussels airport could be a long way off.
The Belgian authorities were hunting two of the Brussels suicide bombers - brothers Khalid El Bakraoui and Brahim El Bakraoui - before the attacks, an article on The Local's France site suggests.
An article published last Thursday says police believed a property used by Paris attacks ringleader Abdelhamid Abaaoud was rented by Khalid El Bakraoui.
It describes him as a "convicted car thief, 27, who is at large", and says his brother was "also known to authorities and served a nine-year sentence in 2010 after firing on police during a robbery".
Police searched the property in the southern Belgian city of Charleroi to verify whether the El Bakraoui brothers were there, "though expectations were low as water and electric power had been cut off for weeks", The Local said.
Speaking on his visit to Argentina, President Obama has said that defeating the Islamic State group (IS) is his number one priority.
He said that his administration was using all the strategies it could to this end, but that he would not employ tactics that were counterproductive.
Mr Obama said it was wrong to think that carpet-bombing Syria or Iraq would help, as it would be inhumane and would help IS attract new recruits.
He also said it would be wrong to discriminate against Muslim communities in America, which he said were well-integrated and patriotic.
I’ve got a lot of things on my plate. But my top priority is to defeat ISIL and to eliminate the scourge of this barbaric terrorism that’s been taking place around the world.
We see high profile attacks taking place in Europe, but they’re also killing Muslims throughout the Middle East. People who are innocent, people who are guilty only of worshiping Islam in a different way than this organisation.
They are poisoning the minds of young people everywhere. Not just in Europe but in the US and undoubtedly in Argentina people are looking at these websites. So there is no more important item on my agenda than going after them and defeating them."
One of the Brussels attackers was deported from Turkey last July, Turkish President Recep Tayyip Erdogan has said.
Turkey reported the deportation to the Belgian authorities, who later set him free, Mr Erdogan said.
The Belgians ignored Turkey's warning that the attacker was a militant, the Turkish president added.
Israeli newspaper Haaretz claims it has learned that the Belgian security services, as well as other Western intelligence agencies, had "advanced and precise intelligence warnings" about planned attacks in Brussels.
Intelligence services knew "with a high degree of certainty" that attacks were planned in the very near future for the airport and, apparently, for the underground railway as well, the newspaper claims.
Haaretz says the attacks were planned in Raqqa, the Islamic State (IS) group's headquarters in Syria. It says the IS cell that attacked Brussels was linked to the cell responsible for the attacks in Paris last November.
The report also says the Brussels attacks were triggered by the arrest of Salah Abdeslam because the jihadists feared he would reveal details of the plans.
The Prime Minister of Poland, Beata Szydlo, has said her country will no longer take in migrants after the Brussels attacks.
Reuters reports that Ms Szydlo told TV station Superstacja:
Twenty-eight EU countries agreed to solve the issue through relocation. But I will say it very clearly: I do not see it possible to allow migrants in Poland at the moment."
Mark Toner, Deputy Spokesperson: for the US State Department, says about a dozen Americans were injured in Tuesday's attacks.
He said the US authorities were not aware of any Americans among the victims, but said a number of US citizens remained unaccounted for.
They include some staff members at the US embassy in Brussels, Mr Toner said.
The embassy is served by the Arts-Lois metro station, a neighbouring station to Maelbeek, where the explosion on the metro train happened.
The Belgian authorities have not yet released nationality information for the reported deaths, Mr Toner added.
London will pay tribute to victims using major landmarks this evening.
Mayor of London Boris Johnson said Londoners would show "solidarity with the people of Brussels"
The BBC's Anna Holligan has spoken to the parents of siblings who are still missing after the attacks.
Their father said he was on the phone to them when the explosion happened.
"It sounded like they fell into a ditch," he said.
Belgian state broadcaster RTBF says it has spoken to the driver of the bombed metro train at Maelbeek station.
Christian Delhasse said at first he thought there had been a technical problem, but he soon he realised it was much more serious. He stopped the train immediately, and began to help victims.
He told the broadcaster: "I did what I had to do. I had nothing, no injuries. I immediately complied with the procedures, it is all I can say."
Seeing the bodies of victims on the ground had left him shocked, he said.
The attack in the subway station left 20 dead and hundreds injured.
Mr Delhasse was back driving trains on Wednesday, the Brussels transport authorities said.