Russia's President Vladimir Putin has condemned Turkey's shooting down of a Russian warplane on its border with Syria.
It is the first time a Russian aircraft has crashed in Syria since Moscow launched air strikes against opponents of President Bashar al-Assad in September.
Both Russia and Turkey say the Russian Su-24, an all-weather attack aircraft, was shot down by Turkish F-16s in the Turkey-Syria border area on 24 November.
Russian President Vladimir Putin said the plane, which had two crew members, was flying at an altitude of 6,000m (19,685ft) when it was hit by an air-to-air missile.
The plane crashed in the mountainous Jabal Turkmen area of the coastal Syrian province of Latakia, which is contested by Syrian government and rebel forces.
Why was it shot down?
In a letter to the UN Security Council, Turkey's permanent representative Halit Cevik wrote that two aircraft whose nationalities were unknown had approached Turkish airspace near the town of Yayladagi in Hatay province.
The planes were warned 10 times over the space of five minutes via an "emergency" channel and asked to change direction, he added.
Both planes disregarded the warnings and then flew 2.19km (1.36 miles) and 1.85km (1.15 miles) into Turkey for 17 seconds from 09:24:05 (07:24:05 GMT).
"Following the violation, plane 1 left Turkish national airspace. Plane 2 was fired at while in Turkish national airspace by Turkish F-16s performing air combat patrolling in the area," Mr Cevik wrote. "Plane 2 crashed onto the Syria side of the Turkish-Syrian border."
The Turkish military also published what it said was the radar image of the path the Russian plane took, showing it briefly flying across Turkey's southern-most tip.
But Mr Putin said the Su-24 was over Syrian territory, 1km (0.6 miles) from Syria's border with Turkey, when it was hit. It crashed 4km from the border, he added.
The Russian defence ministry said the aircraft had remained within Syria's borders throughout its mission. "Analysis of the objective monitoring data definitely showed that there had not been any violation of the Turkish air space," it noted.
US military officials said there were indications the downed plane entered Turkish airspace for a matter of seconds, and that it had been warned to stay out.
What happened to the crew?
Video footage published by Turkish media showed that the Su-24's two crew - the pilot and the navigator/weapon systems officer - ejected as their burning aircraft plummeted to the ground.
A spokesman for a rebel group in the Jabal Turkmen area, the 10th Brigade of the Coast, told the Associated Press that the crew had tried to parachute into government-held territory, but that they came under fire from its fighters.
One of them was dead when he landed on the ground, Jahed Ahmed added.
A video was posted online showing gunmen standing around a man in a flight suit who was immobile on the ground, either badly wounded or dead.
The following day, Russia's defence minister said the second crew member was "alive and well" and had been brought to a Russian airbase in Latakia by Syrian government forces.
A Russian marine was also killed during the attempted rescue mission, when an Mi-8 helicopter he was travelling in came under fire, according to the Russian military.
Why was the Russian jet there?
Russia is one of several countries directly involved in the conflict in Syria, which has left more than 250,000 people dead since March 2011.
Moscow is a staunch ally of President Assad and is conducting air strikes to prop up his government. It says it is targeting only "terrorists" - above all jihadist militants from Islamic State (IS) - but its strikes have mainly hit Western-backed rebels.
Syrian rebels have meanwhile received substantial support from Turkey, an opponent of Mr Assad. Ankara also allows the US-led multinational coalition against IS to use its airbases to conduct strikes on the group in Syria.
How has Russia reacted?
President Putin warned that Tuesday's incident would have "significant consequences" for Turkey, insisting the downed Su-24 had "posed no threat".
He said it had been carrying out "preventative attacks" against Islamic State (IS) in northern Latakia, and accused Turkey of trading with the jihadist group.
"We have long been recording the movement of a large amount of oil and petroleum products to Turkey from IS-occupied territories. This explains the significant funding the terrorists are receiving," he added.
"This was a stab in the back by the accomplices of terrorists."
Although Turkey's policy of allowing rebel fighters and arms shipments to pass through its territory has been exploited by IS, officials have denied supporting the group. Activists say IS has little or no presence in the area around the crash site.
Is Nato backing Turkey?
The Nato military alliance, to which Turkey belongs, called an extraordinary meeting of its main decision-making body, the North Atlantic Council.
Afterwards, Nato Secretary-General Jens Stoltenberg declared: "We stand in solidarity with Turkey and support the territorial integrity of our Nato ally."
"I look forward to further contacts between Ankara and Moscow and call for calm and de-escalation," he added.
The last time a Nato member state shot down a Russian or Soviet plane was reportedly in the 1950s.
Turkish President Recep Tayyip Erdogan warned that "everyone should respect the right of Turkey to defend its borders".
"The reason why worse incidents have not taken place in the past regarding Syria is the cool-headedness of Turkey," he said.
Mr Erdogan also stressed that Turkey's actions were fully in line with the new rules of engagement adopted after Syria shot down a Turkish jet in 2012. The rules state that all "elements" approaching from Syria are considered an enemy threat.