Brussels (AFP) - 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In response, NATO in 2012 deployed Patriot anti-missile batteries in the south but they were due to be withdrawn at the end of this year.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.