NATO chief Jens Stoltenberg said on Tuesday that the military alliance stands by key ally Turkey after it shot down a Russia fighter jet on the Syrian border but urged both sides to try to calm the crisis.

"As we have repeatedly made clear, we stand in solidarity with Turkey and support the territorial integrity of our NATO ally, Turkey," Stoltenberg said after an emergency meeting of all 28 members requested by Ankara.

"I look forward to further contacts between Ankara and Moscow and call for calm and de-escalation. Diplomacy and de-escalation are important to resolve this situation," he said.

Ankara said two of its F16 fighters shot down a Russian Su-24 after it violated Turkish airspace 10 times within five minutes along the Syrian border.

Russia insisted its aircraft was in Syrian airspace.

Stoltenberg said he had warned repeatedly of the dangers posed by Russia's massive air campaign against rebels seeking to oust long-time ally, Syrian President Bashar al-Assad.

"This highlights the importance of having and respecting arrangements to avoid such incidents in the future," he said.

A NATO diplomat said there was strong support for Turkey at the meeting but also calls "for a measured response to ensure this does not happen again".

"This was a serious incident and we don't want it to derail progress made in building a common front against Islamic State," said the diplomat, who asked not to be named.

Turkey is a key NATO member, with the second largest military in the alliance after the United States, and has several times called on its allies for support.

In response, NATO in 2012 deployed Patriot anti-missile batteries in the south but they were due to be withdrawn at the end of this year. NATO said previously the Patriot deployment was being reviewed.

NATO calls 'extraordinary meeting' after Turkey downs Russian jet
Brussels (AFP) Nov 24, 2015 - NATO ambassadors will hold an "extraordinary" meeting Tuesday at Ankara's request to discuss Turkey's shooting down of a Russian fighter jet along the Syrian border, an alliance official said.

"At the request of Turkey, the North Atlantic Council will hold an extraordinary meeting at (1600 GMT). The aim of this extraordinary NAC is for Turkey to inform Allies about the downing of a Russian airplane," the official told AFP.

"NATO is monitoring the situation closely. We are in contact with Turkish authorities."

Ankara said two of its F16 fighters shot down a Russian Su-24 after it violated Turkish airspace 10 times within a five-minute period along the Syrian border. Russia says its aircraft was in Syrian airspace.

The North Atlantic Council consists of ambassadors from the 28 NATO member states. It meets regularly but can be convened into emergency session if one of the allies feels its security is under threat.

But in an apparent sign of caution, Turkey did not request the meeting under NATO's Article Four, under which a member declares that its territorial integrity, political independence or security is under threat.

Ankara did invoke NATO's Article Four back in October to call just such an emergency meeting after Russian planes violated its airspace several times following the start of Moscow's air campaign against Syrian rebels.

On that occasion, the North Atlantic Council warned of "the extreme danger of such irresponsible behaviour" by Russian aircraft.

All 28 NATO members pledge a one-for-all, all-for-one response to any military threat if a member invokes what is known as Article Five when it comes under attack.

The only time Article Five has been invoked was by the United States after the September 11, 2001 attacks on New York and Washington.

Turkey, the second largest military power in NATO after the United States, has invoked Article Four several times as the Syrian conflict has spilled over the border.

In response, NATO deployed Patriot missiles which can shoot down both aircraft and incoming missiles, in the south but they were due to be withdrawn at the end of this year.

NATO said previously the Patriot deployment was being reviewed.