We are going to close our live coverage for the night. You can continue to follow developments via our main story here:
- Turkey says its forces have shot down a plane on the border with Syria
- Russia says an Su-24 crashed on Syrian territory after being hit by an air-to-air missile
- Turkey says the plane violated its airspace – an accusation Russia denies
- President Vladimir Putin calls it 'a stab in the back by the accomplices of terrorists'
- Turkey is a member of the Nato alliance, which has said it is ready to defend Turkey if Russia violated its airspace
Over the course of the day, BBC journalists have been looking at every angle of the downed warplane story:
- Turkey's downing of Russian warplane - what we know
- Was Russia warplane downing an overreaction?
- Video - Putin: Russian jet was shot down over Syria - not Turkey
- Video - Obama: 'Turkey has the right to defend its airspace'
- Video - Turkey's President Erdogan defends downing of Russian warplane
- Who are the Turkmen in Syria?
- Syria crisis: Where key countries stand
- One of the two pilots in the shot-down warplane was killed by gunfire from the ground as he parachuted from the crashing jet, Russian military confirmed
- A Russian soldier was killed when the helicopter he was on came under fire during a search and rescue mission for the pilots
- Nato Secretary General Jens Stoltenberg backed Turkey's version of the story, and said that an allied assessment shows the Russian warplane did fly into Turkish airspace
Washington Correspondent, BBC News
When Russian and US jets came into close proximity over Syria early last month, the Pentagon and the White House were swift to condemn.
"Wreckless" and "irresponsible" were just some of the stiff words they used at the time.
But now that Turkey has actually shot a Russian jet down, there is a tangible reluctance to up the ante, and a scramble to lower the temperature.
Caution is the name of the game, with the Pentagon spokesman, Peter Cook, still saying that the US cannot definitively conclude that Turkish airspace has been compromised.
As a Nato member, Turkey will expect the US and others to back its actions; but with Russia crucial to the prospects of pushing forward a political solution in Syria, de-escalation is the watch word on everyone's lips.
When asked whether the US knows whether the Russian warplane was shot down over Turkey or Syria, Pentagon spokesman Peter Cook said US officers were "not able to conclude definitely right now where the aircraft were".
Echoing those remarks, in an email to the BBC's Gary O'Donoghue, Col Steve Warren, spokesman for the US-led coalition fighting IS, said they were "still analysing the data from the radar tracks".
The US Department of Defense press conference has begun, hosted by spokesman Peter Cook.
The BBC's Gary O'Donoghue has provided some updates from Washington.
The Turkish energy minister, Berat Albayrak, has said that the downing of the Russian warplane does not constitute a threat to energy ties between the two countries.
Turkey is the second biggest purchaser of Russian gas products, according to Gazprom statistics.
We are expecting a press conference with US Department of Defense Spokesman Peter Cook from the Pentagon around 14:30 local time (19:30 GMT).
The BBC's Gary O'Donoghue will be providing updates and analysis on Twitter and this page.
One of the two pilots in the shot-down war plane was killed by gunfire from the ground as he parachuted from the crashing jet, the Russian military has confirmed.
Speaking on Russian state TV, Lieutenant General Sergei Rudskoy also said that Turkish aircraft had violated Syrian airspace when it shot down the warplane.
As we reported earlier, Russian military officials have also said that Syrian rebels fired on a Russian search and rescue helicopter, forcing it to land and killing one crew member.
BBC Monitoring says that the Russian Defence Ministry has issued a statement saying it will step up its operations in Syria, and "discontinue" military contact with Turkey.
Reading the statement on state TV, Lieutenant General Sergey Rudskoy said "measures will be taken to strengthen air defence" and that "any targets representing a potential danger for us will be destroyed".
He said additional weapons will be deployed to the Latakia area.
Writing in Vox, Max Fisher has a counterargument for some of the more apocalyptic assessments of today's events. He says there is little chance of it sparking a wider conflict.
The stakes are just too low. The things at issue here are Russia's bombing of anti-Assad rebels in Syria, the sanctity of Turkish airspace, and the life of one (or possibly two) Russian pilot. Those things matter, and Turkey cares an awful lot about its airspace and about what happens in Syria. But Russia doesn't care enough about those things to risk a major war. And neither do the leading members of Nato (the US, UK, France, etc), which will largely decide how Nato responds. There is thus every reason to believe that both Russia and Nato will seek to de-escalate."
The Russian soldier killed during a search and rescue mission for the crew of the shot-down warplane was on board a helicopter downed by rebel fire, Russia's military has said.
A military spokesman said it was one of two helicopters taking part in the operation. The rest of the crew were evacuated and taken to the air base used by Russia in Syria.
In the last few minutes, Nato Secretary General Jens Stoltenberg has been making a statement in Brussels.
The Nato chief has backed Turkey's version of the story, and said that an allied assessment shows that the Russian warplane did fly into Turkish airspace.
He said that there had been contact between officials in Moscow and Ankara, but not between Nato officials and Russia.
Mr Stoltenberg called for calm and for the parties to deescalate the situation.
A Russian soldier has been killed in the search for the pilots of the downed jet in Syria, the Russian military says.
In his first reaction to his forces' downing of a Russian jet, Turkish President Recep Tayyip Erdogan said "everyone should respect the right of Turkey to defend its borders".
Alpaslan Celik, a deputy commander in a Syrian Turkmen brigade, holds the handles of what is believed to be part of a parachute used when the Russian warplane was shot down.
Echoing some of Mr Obama's comments, Francois Hollande said "we must prevent an escalation that would be extremely damaging.
"The only purpose is to fight against terrorism and Daesh (Islamic State).
"What took place means that we must find a solution to the Syrian crisis, otherwise there are risks of escalation."
The president adds that he will be travelling to Russia this week.
"I do think this points to an ongoing problem with Russian operations (in Syria)," Mr Obama continued, "in the sense that they are operating very close to a Turkish border and they are going after moderate opposition."
"If Russia is directing its energies towards Daesh and Isil (Islamic State), some of those conflicts or potentials for mistakes or escalation are less likely to occur."
Asked about the downing of a Russian jet, President Obama said he was still getting the details. But he said "Turkey, like every country, has the right to defend its territory and its airspace".
He went on to say it was important for the Russians and Turks to talk to each other and take measures to "discourage escalation".
UN Secretary General Ban Ki-moon says he is "seriously concerned" about the downing of the Russian jet and has appealed to all parties to urgently de-escalate, Reuters reports.
In a letter to the UN security council and Secretary General Ban Ki-moon, Turkey's UN ambassador Halit Cevik said two planes approached Turkish airspace on Tuesday morning.
He said they were warned 10 times in five minutes to change direction.
"Following the violation, plane one left Turkish national airspace. Plane two was fired at while in Turkish national airspace by Turkish F-16s performing air combat patrolling in the area," Mr Cevik wrote in a letter, Reuters reports.
"Plane two crashed onto the Syria side of the Turkish-Syrian border," he said.
Russian President Vladimir Putin has said the fighter jet was attacked when it was nearly a mile inside Syria and has warned of "serious consequences".
We are following a live statement from President Obama, who is speaking after talks with French counterpart Francois Hollande. The president has not commented yet on the downing of a Russian jet, but said the two men agreed that "Russian strikes against moderate (Syrian) opposition only bolsters the Assad regime, whose brutality has helped fuel the rise of Isil (Islamic State)".
The Russian Defence Ministry website has more details on the Sukhoi Su-24 jet, the type shot down by Turkey. It is primarily used as an all-weather, low-level bombing aircraft.
- Dimensions: Length 24.5m, height 6.2m
- Weight: 19,000kg, but normal take-off weight is 36,000kg
- Max speed at high altitude: 2,240 km/h (1391 mph)
- Combat radius: Up to 560km, i.e. how far it can travel to before returning back on a mission
Barely distinguishable, but this still taken from Turkish television appears to show two parachutes after the Russian jet was shot down.
BBC Diplomatic and defence correspondent
But as the Russian air attacks against Turkmen positions show, Moscow is still intent on bolstering the Assad regime against some of its other opponents, whatever may be happening on the counter-IS front.
Turkey is deeply hostile to the Syrian regime and wants to see the back of Bashar al-Assad as soon as possible. So in this sense it is at loggerheads with Moscow.
Turkey, like Iran, the Saudis and the moderate Arab states, all have a stake in what kind of Syria emerges from this crisis - as, to an extent, does Russia.
The US and its Western allies don't much like Mr Assad and see him as very much part of the problem, but their main battle is against IS.
Turkey's Hurriyet website reports Russia's ambassador to Turkey and the military attache were summoned to the Foreign Ministry last Thursday because of the following allegations:
- The operations of the Russian army were taking place in areas very close to Turkey's border, threatening its border security. Turkey noted its rules of engagement were in place and there would be no hesitation to implement them if a violation occurred.
- The area where Russian operations were being conducted was free of Islamic State and other terrorist groups and civilian Turkmen were being harmed.
- Military operations were causing more civilians to leave their homes. There was concern Russia's operations in that particular region could hurt Turkey's humanitarian efforts.
British Prime Minister David Cameron has discussed the incident with his Turkish counterpart, Downing Street says.
In it he encouraged the Turks and the Russians to have a "direct conversation" over the matter. Mr Cameron is due to make the case for British jets to carry out strikes in Syria on Thursday.
The Russian Defence Ministry has summoned the Turkish embassy defence attache to make a protest, the ministry has said in a statement published on its website.
"The Russian plane did not cross the Turkish border and operated exclusively against facilities in Syrian territory. We consider the actions of the Turkish Air Force to be an unfriendly act,"the statement reads [in Russian].
Germany's Foreign Minister, Frank-Walter Steinmeier, says he hopes the incident will not hamper fresh talks over the Syria crisis.
"I hope first that both capitals start talks with each other and that second, both Ankara and Moscow are aware of the responsibility when it comes to reactions and couter-reactions," he says.
The BBC's Moscow Correspondent, Sarah Rainsford, has been considering President Putin's furious speech earlier, in which he called Turkish action a "stab in the back" and called them "accomplices of terrorists".
This was tough language from an icy looking President Putin. Much of his comment was for domestic consumption. After all, Vladimir Putin launched airstrikes in Syria arguing that it would make Russia safer; instead, 224 people were blown out of the sky last month in a bomb attack. And now this. By rounding on Turkey he is in part deflecting any suggestion that his own policy has backfired. But he is clearly furious too and it’s not clear yet how that will translate into action."
Chechen leader Ramzan Kadyrov has promised Turkey will "regret what it has done for a very long time", in a statement posted on his Instagram page and quoted on the website of pro-Kremlin LifeNews.
"Those who take every opportunity to talk about friendship and cooperation should not act so underhandedly," Mr Kadyrov added.
A spokesman for the US-led coalition against Islamic State, Col Steve Warren says it can confirm that the Turks warned the Russian plane 10 times before shooting down the jet.
He said they were working to establish exactly where the plane was when it was shot down.
The conflict in Syria has drawn in major global powers, supporting and opposing President Bashar al-Assad and the myriad rebel groups ranged against him.
This shows the various factions at work and the territory where they operate.
Here's a guide to where the key countries stand on the strategy regarding Syria.
Turkey's President, Recep Tayyip Erdogan, is to chair a security summit later on Tuesday following the downing of the Russian fighter jet.
It will be attended by armed forces and intelligence chiefs.
To put the previous posts in context, a sharp reduction in Russian tourists visiting Turkey could have a big impact. Recent figures from the Turkish authorities suggest Russians are the second biggest visitors by nationality.
Natali Tours, one of Russia's largest tour operators, has suspended the sale of package holidays to Turkey,news website Gazeta.rureports [in Russian].
According to a press release from the company, the decision is based on President Vladimir Putin's decree of 8 November announcing measures aimed at "ensuring the safety of Russian citizens".
Russian Foreign Minister Sergei Lavrov has advised Russians not to visit Turkey and said the threat of terrorism there was the no less than in Egypt, where a Russian passenger plane was brought down last month.
Our colleagues at BBC Monitoring have been taking a look at the Turkmen, with fighters from the community claiming they shot dead the two fighters who ejected from the downed Russian plane.
Who are they? Ethnic Turks who have lived in the region of Syria, Iraq and Iran since the 11th century. They are estimated to number between 1.5m and 3.5m.
What is their role in Syria? Trained by Turkey, the Syrian Turkmen Brigades are about 10,000 strong and were set up in 2012 as the civil war in Syria took hold.
Who are their allies/enemies? Their main opponents are the regular Syrian army and the Islamic State militant group. Some units have allied with Kurdish fighters.
Russian Foreign Minister Sergei Lavrov has cancelled a visit to Turkey on Wednesday, agencies report.