Another group of Russian warplanes have left their air base in Syria to return home, Russia's defence ministry has said.

The announcement comes two days after President Vladimir Putin ordered the Russian military to withdraw most of its fighting forces from Syria, signalling an end to Russia's five-and-a-half-month air campaign.

The pullout from the Hemeimeen base coincides with the resumption of UN-brokered peace talks in Geneva between the Syrian government and representatives of the moderate, Western-backed opposition.

On the ground, a ceasefire has been in effect since late February. Extremist factions - such as the Islamic State group or the al Qaida-linked Nusra Front - are not part of the truce.

Russia did not indicate when the next group of planes will leave or how many will be pulled out.