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
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 , externalwebsite 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.
Image source, ReutersBarely distinguishable, but this still taken from Turkish television appears to show two parachutes after the Russian jet was shot down.
Image source, AP
Jonathan Marcus
BBC Diplomatic and defence correspondent
The downing of the Russian airliner by IS, and Moscow's onslaught against IS targets appeared to suggest that Russia, the West and the moderate Arab states were coming into alignment.
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.
Image source, AFPTurkey 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, external reports Russia's ambassador to Turkey and the military attache were summoned to the Foreign Ministry last Thursday because of the following allegations:
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.
BBC Monitoring
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]., external
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.
Image source, AFPThe 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".
Quote MessageThis 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."
BBC Monitoring
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., external
"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.
Image source, EPAIt 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.
BBC Monitoring
Natali Tours, one of Russia's largest tour operators, has suspended the sale of package holidays to Turkey,news website Gazeta.rureports [in Russian], external.
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.
Image source, EPAA Russian A321 airliner was brought down in in Egypt last month, killing all 224 people on board
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.
Image source, AFPRussian Foreign Minister Sergei Lavrov has cancelled a visit to Turkey on Wednesday, agencies report.
Image source, EPA