Russian warplanes have arrived home from Syria as opposition negotiators demanded the Government detail its thoughts on a political transition.
The planes left after Moscow on Tuesday said it would start to withdraw forces. Russia has tipped the war President Bashar al-Assad's way.
The development came as peace talks were being held in Geneva. The opposition High Negotiations Committee used its first meeting in the round of peace talks to give United Nations mediator Staffan de Mistura a set of general principles to guide the transition, a process to be overseen by Russia and the United States in line with a UN resolution.
"We intend to go into detail. We intend to go fast. We would like to see this process make progress very quickly," HNC member Basma Kodmani said after the meeting.
She said the delegation had raised concerns about the humanitarian situation, particularly in the towns of Daraya, where "after four years there still is no aid at all that has gone in", and Al Waer in Homs governorate.
The opposition also wanted the Government to set out how it would begin releasing prisoners, she said.
Meanwhile, Russian television showed the first group of Su-34 jets landing at a base in the south of Russia. The pilots were greeted by 200 to 300 servicemen, journalists, and their wives and children, waving Russian flags, balloons in red, white and blue, and flowers.
They were mobbed and thrown in the air by the crowd. A brass band played Soviet military songs and the national anthem. Two priests paraded a religious icon.
UN envoy de Mistura called President Vladimir Putin's surprise move a "significant development" towards resolving the conflict which this week passes its fifth anniversary.
Assad's opponents hope Putin's announcement signalled a shift in his support. However, its full significance is not yet clear: Russia is keeping an air base and forces in Syria.
Russian jets were in action against Isis (Islamic State) yesterday. Assad also still enjoys military backing from Iran, which has sent forces to Syria along with Lebanon's Hizbollah.
Russia said last month Assad was out of step with its diplomacy, prompting speculation Putin was pushing him to be more flexible at the Geneva talks, where Assad's Government has ruled out discussion of the presidency or a negotiated transfer of power. AAP