Turkey shot down a Russian warplane on the Syrian border on Tuesday, causing international powers to plead for calm as tensions soared between the two rival players in the Syria war.

Russian President Vladimir Putin slammed Ankara as "accomplices of terrorists" while the Russian military announced it would cease all military contact with Turkey.

Moscow said one of two pilots who ejected from the Su-24 plane was killed by gunfire from the ground as he descended, although Turkish officials insisted both were still alive.

A Russian soldier was also killed when a helicopter search-and-rescue operation came under fire, the Russian defence ministry said.

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.

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.

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 stab in the back' -

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.

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. The other members of the squad were successfully evacuated.

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 Wednesday while 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 (2.5 miles) from the border and "did not in any way threaten Turkey".

Russian military spokesman Rudskoi warned the shooting down would have the "the gravest consequences" and noted Russia's Moskva guided missile cruiser would be stationed near the Syrian Mediterranean port of Latakia.

"All targets representing a potential threat to us will be destroyed," he said.

- 'Turkey like Egypt' -

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 held an extraordinary meeting to discuss the incident.

"Diplomacy and de-escalation are important to resolve this situation," said NATO chief Stoltenberg.

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.