UPDATED 9.47pm: US President Barack Obama has declared support for Turkey's right to defend its sovereignty.

LISTEN: Al Gillespie: Russia/Turkey relations

Russia continues to insist its warplane was not in Turkish airspace when it was shot down by Turkey yesterday.

Russian president Vladimir Putin said its a stab in the back by Turkey, and the Russian pilots had no warning the attack was coming.

The BBC's Sarah Rainsford is in Russia, and said Mr Putin remains adamant the plane was in Syrian airspace.

She said Russia is claiming the pilots were carrying out a heroic battle against Islamic State militants on the ground.

One pilot was shot dead as he attempted to parachute to safety from his burning plane.

MORE: Turkey shoots down Russian fighter jet on Syrian border

With alarm growing that the incident could snowball into a major conflict, Russian President Vladimir Putin slammed Ankara as "accomplices of terrorists".

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US President Barack Obama said Turkey had "a right to defend its territory and its airspace" but urged against any escalation, while NATO chief Jens Stoltenberg also called for calm.

Analysts said the incident risks derailing efforts to bring peace to Syria that were gaining tentative momentum following the November 13 Paris terror attacks, claimed by Islamic State militants who control swathes of northern Syria.

The Turkish army said the fighter was shot down by two of its F-16s after it violated Turkish airspace 10 times within a five-minute period.

A US military spokesman in Baghdad confirmed that 10 warnings had been issued, but said it was not immediately clear on which side of the border the jet had been flying, and it would take some time to analyse data before knowing for sure.

Moscow insisted that the jet had stayed inside Syrian territory, and Damascus denounced the incident as "flagrant aggression" against Syrian sovereignty.

Turkish television pictures showed the Su-24 exploding and crashing in a ball of flames into a Syrian mountain and two pilots parachuting to the ground after ejecting.

A Turkish government official had earlier insisted both pilots were still alive, but Russian military spokesman General Sergei Rudskoi said one had been killed by fire from the ground, citing "preliminary details".

The fate of the second pilot was unknown. Rudskoi said a soldier had been killed in a failed bid to rescue the pair after one of his squadron's helicopters was damaged by gunfire and had to land.

Sources had told AFP in Beirut that a Russian helicopter in the same area was destroyed by rebels on the ground after being forced to make an emergency landing but its personnel were then evacuated by Syrian special forces.

The shooting down of the Russian plane is the first of its kind since Moscow launched air strikes in Syria in September in support of President Bashar al-Assad's regime, causing concern in the West over a possible clash with US-led coalition planes also in the skies.

Russian Foreign Minister Sergei Lavrov scrapped a planned visit to Turkey on Wednesday while President Vladimir Putin branded the shooting down of the aircraft a "stab in the back committed by accomplices of terrorists".

He said oil from jihadist-controlled territory was exported through Turkey while funding was sent the other way, and warned: "The tragic event will have serious consequences for Russian-Turkish relations."

Putin said the plane fell in Syrian territory four kilometres from the border and "did not in any way threaten Turkey".

The Turkish army said the downing took place over the Yayladagi district of Hatay province on the border with Syria after the "plane violated Turkish air space 10 times in five minutes despite warnings."

"Everyone must respect the right of Turkey to protect its borders," President Recep Tayyip Erdogan said in his first official reaction to the downing of the war plane.

CNN-Turk television said Syrian Turkmen forces fighting the Damascus regime had captured one of the pilots while Syrian opposition sources told AFP one had been killed by rebels and the second was missing.

The incident comes as Russian and Syrian jets wage a heavy bombing campaign against targets in northern Syria while the US-led coalition continues its own air strikes.

Turkey has expressed anger at the operation, saying it is aimed at buttressing the Assad regime and has displaced thousands of Turkmen Syrians, an ethnic minority in the area and strong allies of Ankara.

Turkey and Russia have long been at loggerheads over the Syrian conflict, with Ankara seeking Assad's overthrow while Moscow does everything to keep him in power.
Russia however insists its strikes are aimed against IS.

At Ankara's request, NATO allies will hold an "extraordinary" meeting to discuss the incident.

Russian fighter jets entered Turkish airspace in two separate incidents in October while Turkey also shot down a Russian-made drone that had entered its airspace.

As well as cancelling his visit to Turkey, Lavrov warned Russians against travel to the country, which would be a huge blow for the Turkish tourism industry.

He said the risk of attacks "is no less of a threat than in Egypt" where all 224 people onboard a Russian passenger jet were killed in October in an attack claimed by IS

UN calls for urgent measures to de-escalate tensions

UN Secretary-General Ban Ki-moon on Tuesday called for urgent measures to de-escalate tensions.

Ban said a "credible and thorough review" of the incident would help clarify what happened and prevent a repeat.

"The secretary-general urges all relevant parties to take urgent measures with a view to de-escalate the tensions," said UN spokesman Stephane Dujarric.

The Russia SU-24 attack plane was shot down earlier Tuesday by two Turkish F-16s after it received 10 warnings within a five-minute period, Turkey's envoy to the UN said.

The US military backed up Turkey's claim that Turkish pilots warned a Russian jet 10 times, but failed to get a response, before shooting it down after it briefly entered Turkish airspace.

Turkish ambassador Halit Cevik said in a letter to the UN Security Council that his government was determined to defend its sovereignty, security and borders.

"Our rules of engagement are well known and are reiterated to all parties on numerous occasions," wrote Cevik.

"Turkey will not hesitate to exercise its rights emanating from international law to protect the security of its citizens and borders."

The ambassador said two SU-24 planes approached Turkish airspace in the Hatay region, flying at an altitude of 19,000 feet and that they crossed into Turkish airspace for 17 seconds.

"Despite these warnings, both planes... violated Turkish national airspace to a depth of 1.36 miles and 1.15 miles in length for 17 seconds" from 9.24am local time, wrote the ambassador.

One plane left Turkish air space, but the second one was fired at by Turkish F-16s performing patrols in that area, said the ambassador.

Russia insisted the fighter jet was inside Syrian territory and President Vladimir Putin warned of "serious consequences" for Russian-Turkish relations.

British ambassador Matthew Rycroft, whose country chairs the council this month, said a meeting could be held if requested and that the incident was not raised during a morning session.

Rycroft said he was "extremely concerned" and stressed the importance of "deconfliction" measures to prevent clashes in the air campaigns being waged by Russia and the US-led coalition in Syria.