Russia's military says it has begun scaling down its deployment to Syria with its sole aircraft carrier the first to quit the conflict zone.

President Vladimir Putin ordered the reduction of forces in Syria on December 29 as he announced a ceasefire between government and rebel forces, which has since dampened down the fighting.

"In accordance with the decision of the supreme commander of the Russian armed forces, Vladimir Putin, the Russian defence ministry is beginning the reduction of the armed deployment to Syria," Russian news agencies quoted military chief Valery Gerasimov as saying on Friday.

Gerasimov said the naval group headed by Moscow's sole aircraft carrier - Admiral Kuznetsov - would be the first to leave the area.

"The tasks set for the aircraft carrier group during its military mission have been fulfilled," said Andrei Kartapolov, Russia's main commander in Syria.

Kartapolov said Russia still had sufficient air defence capabilities in Syria thanks to its S-300 and S-400 systems deployed in the war-torn country.

Putin announced a partial withdrawal of Russian forces in March 2016, but Moscow later had to ramp up its military presence again as fighting intensified.

Russia boosted its firepower on land in Syria and off the coast in the Mediterranean Sea in September 2015 in support of government forces targeting the country's second city of Aleppo and other locations.

The military deployment helped turn the tide in favour of the Syrian government's ailing forces.

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Russian bombardment, however, has been blamed for thousands of civilian deaths.

Troops loyal to Russia's ally Bashar al-Assad ousted rebels from Aleppo last month in their biggest victory in nearly six years of fighting, paving the way for the Kremlin to launch a new push for a political solution to the conflict, which has killed hundreds of thousands of people.

Russia - along with Turkey and Iran - are pushing for peace talks to be held later this month in the capital of Kazakhstan, Astana.