Russia is to deploy its newest anti-aircraft missile system to Syria following the shooting down of one of its fighter jets by Turkish warplanes.
Defence minister Sergei Shoigu said the S-400 missiles would be stationed at the Hemeimeem air base from where Russia is conducting its aerial bombing campaign in support of the regime of President Bashar Assad.
The move came as President Vladimir Putin confirmed that one of the pilots of the Su-24 aircraft had been rescued by Syrian army forces and brought to safety at the base.
Russia said the other member of the two-man crew was killed by ground fire from "jihadists" after ejecting from the stricken jet close to the Syria-Turkey border on Tuesday.
In a statement, the Syrian armed forces said Syrian and Russian forces had penetrated into territory controlled by the "terrorists" - the regime's description of all armed opposition - to rescue the pilot.
With world leaders calling for calm, Turkish president Recep Tayyip Erdogan insisted that he was not seeking to escalate tensions with Moscow.
Speaking at a meeting of the Organisation of Islamic Co-operation in Istanbul, he said that his country wanted "peace, dialogue and diplomacy".
At the same time, however, he strongly defended the shooting down of the Su-24, warning "no one should expect Turkey to stay silent to border violations or the violation of its rights".
Russia has vehemently disputed Ankara's claims that its aircraft crossed into Turkish airspace in the course of the bombing mission, insisting that it remained on the Syrian side of the border throughout its flight.
A furious Mr Putin warned of "significant consequences" for an attack which he described as a "stab in the back by the terrorists' accomplices".
Nato and the United States called for "de-escalation" amid fears the fallout from the incident could spiral into further confrontations in a highly volatile arena.
It comes as a further complication for David Cameron as he prepares to set out the case for RAF warplanes to join the air strikes on Islamic State (IS) extremists is Syria in a Commons statement on Thursday.
The Prime Minister has urged his Turkish counterpart to ensure that Ankara maintains direct communications with Moscow to avoid any heightening in tensions.
Downing Street said that Ahmet Davutoglu had phoned Mr Cameron on Tuesday to explain that Turkey had taken protective action after the Russian jet was warned "several times" not to violate its air space.
Following an emergency meeting in Brussels on Tuesday, Nato said it "stands in solidarity" with Turkey and called for "calm" after holding an emergency session in response to the incident.
Secretary general Jens Stoltenberg said assessments provided by other alliance members were consistent with Turkey's claims that the Su-24 had violated its airspace.
US president Barack Obama said: "It's very important right now for us to make sure that both the Russians and the Turks are talking to each other, find out exactly what happened, and take measures to discourage any kind of escalation."
It is thought to be the first time a warplane from a Nato member has shot down a Russian aircraft in half a century.