A Russian marine has been killed on a helicopter mission to rescue the crew of a jet downed by Turkey close to the Syrian border on Tuesday.
He died when his helicopter came beneath fire from rebels in northern Syria, where the plane crashed.
Rebel fire from the ground killed a single of the jet’s two crew members soon after they ejected.
The head of Nato stated it stood in solidarity with Turkey as the Kremlin warned of “significant consequences”.
Turkey mentioned the jet had strayed into its airspace but Russian President Vladimir Putin insisted the Su-24 had been hit by an air-to-air missile even though flying over Syrian territory.
Nato’s Secretary Common Jens Stoltenberg said he backed the Turks’ assessment.
“We stand in solidarity with Turkey and assistance the territorial integrity of our Nato ally, Turkey,” he said soon after an emergency meeting of the bloc. But he also named for each sides to de-escalate the circumstance.
President Putin described the downing of the plane as a “stab in the back”.
Breaking off military contacts with Turkey, Russia’s defence ministry said a cruiser equipped with an air defence program would be deployed in the Mediterranean to destroy “any targets representing a possible danger” for Russian forces in Syria.
Russian bombers carrying out air strikes more than Syria will now be escorted by fighters, the military stated.
Analysis: Mark Lowen, BBC Turkey correspondent
Following Turkey became the 1st Nato member to shoot down a Russian plane in over half a century, the question now is how will Moscow respond?
President Putin named Turkey an “accomplice of terrorists” and Foreign Minister Sergei Lavrov cancelled a planned trip to Ankara on Wednesday.
But the UN and Nato have urged both sides to de-escalate the crisis. According to Ankara, the Russian Su-24 was warned ten times about entering Turkish airspace, although Moscow says there was no such communication.
But Turkey also stated the violation lasted just seventeen seconds. And offered signs that a united front was starting to kind against Islamic State, there will be diplomatic pressure on both sides to concentrate alternatively on the common threat from the militants.
The difficult talk from Ankara and Moscow will no doubt continue – but regardless of whether there will be critical retaliation is less clear.
Russian defence official Lt-Gen Sergey Rudskoy said the rest of the rescue group, which had been using two Mi-8 helicopters, had been safely evacuated from the area to Russia’s Humaymim air base close to Latakia in Syria.
“For the duration of the operation, one of the helicopters came below tiny-arms fire, was broken and created an emergency landing on neutral territory,” he said.
“One particular naval infantryman serving below contract was killed.”
A single of the helicopters was destroyed on the ground by “mortar fire” following generating an emergency landing, the Russian general stated.
Syrian rebels say they blew up the helicopter shortly after it landed with an anti-tank missile, releasing footage of the attack.
The fate of the Russian jet’s other crew member remains unknown.
Russians have been advised not to visit Turkey – a common tourist location – with Foreign Minister Lavrov saying the terror threat there was no significantly less than in Egypt, where a bomb attack brought down a Russian passenger plane final month.
One particular of Russia’s largest tour operators, Natali Tours, has suspended package holidays to Turkey.
Turkish President Recep Tayyip Erdogan said his forces had been acting inside its guidelines of engagement.
“Everyone must respect the right of Turkey to defend its borders,” he said.
The US, the EU and the UN have all appealed for calm.
President Obama said it was essential to uncover out precisely what had occurred and to take measures to “discourage any type of escalation”.
But he mentioned the incident pointed to an “ongoing difficulty” with Russian action in Syria, saying if Russia had been targeting IS, rather than “moderate” Syrian opposition forces, such incidents would be unlikely.
Russia and Turkey have found themselves on opposing sides in Syria’s conflict, with Russia supporting its ally President Bashar al-Assad and Turkey calling for his ousting.