Russian warplanes leave Syria, raising UN hopes for peace talks

As the first aircraft touched down in Russia, U.N. envoy Staffan de Mistura called President Vladimir Putin's surprise move a "significant development" toward resolving a conflict which this week passes its fifth anniversary.

Assad's opponents hope Putin's announcement on March 13 that most Russian forces would be withdrawn signaled a shift in his support. However, its full significance is not yet clear: Russia is keeping an air base and undeclared number of forces in Syria.

Russian jets were in action against Islamic State on March 15. Assad also still enjoys military backing from Iran, which has sent forces to Syria along with Lebanon's Hezbollah.

Russia said last month Assad was out of step with its diplomacy, prompting speculation Putin is pushing him to be more flexible at the Geneva talks, where his government has ruled out discussion of the presidency or a negotiated transfer of power.

Damascus has dismissed any talk of differences with its ally and says the planned withdrawal was coordinated and the result of army gains on the ground.

British Foreign Secretary Philip Hammond, whose government supports the opposition, indicated the gaps in Western understanding of Putin, saying he had "no insight at all into Russia's strategy" after a decision that came out of the blue.

The West had been equally surprised by Putin's decision to intervene. "Unfortunately none of us knows what the intent of Mr Putin is when he carries out any action, which is why he is a very difficult partner in any situation like this," Hammond said.

Analysts in Moscow said Putin's acquisition of a seat at the diplomatic top table may have motivated his move to scale back his costly Syria campaign.