A man has been arrested on suspicion of terror offences after he drove a van into a group of worshippers close to a mosque in north London.
One man, who had taken ill before the attack began, died and nine others were taken to hospital, some of whom were critically injured.
The terror attack happened shortly before 00:20 BST on Monday, 19 June, when the vehicle mounted the pavement outside Muslim Welfare House - which is also a community centre - on Seven Sisters Road.
Here is what we know so far.
A number of worshippers from Muslim Welfare House and nearby Finsbury Park Mosque were on the streets at the time, having just taken part in evening prayers after breaking the Ramadan fast.
A group were helping an elderly man who had fallen down in Whadcoat Street - a short road off Seven Sisters Road - as they waited for their next set of prayers.
It was then that a white van came down the street, mounted the pavement and drove into people.
Calls were made to the emergency services at about 00:20 BST. A police van arrived within one minute and a cordon was raised around the area within 10 minutes.
The man who was driving the van was restrained by people at the scene, and an imam stopped some of the crowd from attacking the suspect.
More than 60 medics went to help the injured, including ambulance crews, advance paramedics, specialist response teams, and a trauma team from London's Air Ambulance.
Prime Minister Theresa May said the attack was "declared a terrorist incident within eight minutes" of the first emergency call being received.
As a result, officers from the local borough are being supported by armed police and the Territorial Support Group, which is deployed to events that may involve public disorder. The Counter Terrorism Command is leading the investigation.
Who were the victims?
Police confirmed early on Monday that the elderly man who was receiving first aid before the attack had later died.
He has not yet been named, and police said they were still investigating whether he died as a result of the attack or something else.
The London Ambulance Service said nine people were being treated in three hospitals in the capital, with some in a serious condition.
Two other people were treated at the scene for minor injuries.
The police confirmed that all the victims were Muslims.
Witnesses reported seeing one man giving CPR to a victim in the street, while another man's head injury was treated with a makeshift dressing.
Who was the attacker?
The BBC understands Darren Osborne, a 47-year-old man from the Cardiff area, was initially arrested on suspicion of attempted murder. He grew up in Weston-super-Mare in Somerset and has four children.
He was later also arrested for the commission, preparation or instigation of terrorism.
Immediately after the attack he was detained by members of the public as they waited for police to arrive on the scene.
Eyewitness Abdul Rahman told the BBC: "When the guy came out from his van he wanted to escape, run away, and he was saying 'I want to kill Muslims. 'I want to kill Muslims.'"
Police said he was taken to hospital as a precaution. Security minister Ben Wallace said the man was not known to the police or security services, and it is thought he acted alone.
Some witnesses said there was more than one person involved in the attack, but a statement from the police said there were no other suspects.
Forensics officers are now examining the white van, which has Pontyclun Van Hire - a firm from Rhondda Cynon Taff in Wales - written on it.
A residential address in the Cardiff area is being searched in relation to the terror attack.
Mr Osborne's family released a statement, which said: "We are massively in shock, it's unbelievable. It still hasn't really sunk in.
"We're devastated for the families, our hearts go out to those who've been injured.
"It's madness, it must just be complete madness."
What has the reaction been?
Mrs May said the incident was a terror attack. She said the man arrested on suspicion of carrying out the attack "targeted the ordinary and the innocent going about their daily lives".
She reiterated remarks that were made after an attack near London Bridge, saying "there has been far too much tolerance of extremism over many years."
She added that there would be nowhere left for extremism to hide.
Labour leader and local MP Jeremy Corbyn said on Twitter that he was "totally shocked" by what had happened.
"I've been in touch with the mosques, police and Islington council regarding the incident. My thoughts are with those and the community affected by this awful event."
Mayor of London Sadiq Khan promised additional policing to reassure communities, especially those observing Ramadan. He has also asked people to "remain calm and vigilant".
"We don't yet know the full details, but this was clearly a deliberate attack on innocent Londoners, many of whom were finishing prayers during the holy month of Ramadan," he said.
"While this appears to be an attack on a particular community, like the terrible attacks in Manchester, Westminster and London Bridge, it is also an assault on all our shared values of tolerance, freedom and respect."
Imam Mohammed Mahmoud, who protected the alleged attacker from an angry crowd, said: "This demonisation of the Muslim community at the hands of people with ulterior motives... have succeeded to some extent [by] influencing the vulnerable and the impressionable.
"It's on a par with the London Bridge attack... and we just hope that in times of tragedy people come together and unite.
"The fabric of this society is not torn but we have to continue to keep the fabric of this society intact, and come together."
General secretary of the Finsbury Park mosque Mohammed Kozbar said: "An attack on one faith is an attack on all faiths and communities.
"They will try to divide us... they will not succeed."
The secretary general of the Muslim Council of Britain (MCB), Harun Khan, tweeted that the van had "intentionally run over worshippers" and that he was "shocked and outraged".
In a statement, the MCB added that it was a "violent manifestation of Islamophobia" and called for extra security around mosques.
Communities Secretary Sajid Javid spoke briefly to concerned residents before being led through the police cordon as he visited the scene. He said "the attacker will not succeed in his efforts to divide British society".
The Jewish Community Council of North London called the attack "barbaric" and tweeted that members shared their "thoughts and prayers with our friends and neighbours".
Speaking on his first state visit as Irish prime minister, Taoiseach Leo Varadkar said: "I think pretty much everyone in Ireland has somebody who lives [in London] who's a relative or a close friend.
"And when there's an attack on London, we feel in Ireland that it's almost an attack on us as well."
Police have asked witnesses or anyone with information to call them on 101 or contact them via Twitter @MetCC.
Information can also be provided anonymously by calling Crimestoppers on 0800 555 111 or visiting its website.