Vladimir Putin has announced that Russian troops will begin a partial withdrawal from Syria, in a surprise move that could herald a major shift in the conflict.

In a claim given a wary welcome by the Syrian opposition, the Russian President said that his five-month military campaign in support of President Bashar al-Assad had “achieved its aims”, and ordered his Foreign Minister to “intensify” Moscow’s role in peace talks that have resumed in Geneva.

Announcing his decision in a televised meeting with ministers at the Kremlin, Mr Putin said he had ordered the withdrawal of “the main part of our military contingent” but said a Russian airbase and naval facility in the country would continue to operate.

A Syrian boy carrying another injured boy away from the scene of a Russian air strike in Damascus in December 2015 (Getty)

The announcement comes as Syria marks the fifth anniversary of the uprising against President Assad. Moscow has been one of the staunchest allies of Damascus, and the Russian military intervention at the end of September shifted the momentum in the conflict in its favour.

The presidential spokesman, Dmitry Peskov, said that Mr Assad had agreed to the decision following a telephone conversation with Mr Putin. Syria’s state news agency quoted the Syrian President as saying that the collaboration between Russian and Syrian forces has secured “victories against terrorism and returned security to the country”.

While its intervention was officially launched to combat terrorist groups, Russia has been widely accused of using a relentless air campaign to target more moderate rebel groups as well as hundreds of civilian targets including schools and hospitals.

The latest announcement will be met with cynicism in Western capitals, where diplomats say that Mr Putin has proved to be a mercurial and untrustworthy partner not just in the Syria conflict but also in the war in Ukraine.

Mr Putin said that the withdrawal would begin on Tuesday but did not give a timeline for completion, nor did he specify how many planes and troops would be pulled out. Russia’s airbase in Hmeymim, in Syria’s coastal Latakia province, and its naval facility in the Syrian port of Tartous would remain, he said. Russia’s UN ambassador said that Russia would continue the fight against “terrorists” – a term it has used to describe all those opposed to President Assad.

The official Syrian opposition, which had no prior warning, offered a cautious welcome. It said that, if implemented, a withdrawal would pile pressure on the Syrian government and give new impetus to the drive to reach a negotiated settlement.

Salim al-Muslat, spokesman for the rebel High Negotiations Committee, said: “If this is a serious step it will form a major element of pressure on the regime, because the Russian support prolonged the regime. Matters will change significantly as a result of that.”

The US also said that it had no advance knowledge of the announcement. A spokeswoman for the United Nations Syria envoy, Staffan de Mistura, refused to say whether he was aware of plans. Earlier in the day, Mr de Mistura warned that the only alternative to negotiations was a return to war. He is due to brief the UN Security Council on the developments from Geneva on Monday night.

In pictures: Russian air strikes in Syria Show all 19 1 /19 In pictures: Russian air strikes in Syria In pictures: Russian air strikes in Syria Syrian boys cry following Russian air strikes on the rebel-held Fardous neighbourhood of the northern embattled Syrian city of Aleppo Getty In pictures: Russian air strikes in Syria Russian defense ministry spokesman Major General Igor Konashenkov speaks to the media in Moscow, Russia. Konashenkov strongly warned the United States against striking Syrian government forces and issued a thinly-veiled threat to use Russian air defense assets to protect them AP In pictures: Russian air strikes in Syria Syrians wait to receive treatment at a hospital following Russian air strikes on the rebel-held Fardous neighbourhood of the northern embattled Syrian city of Alepp Getty In pictures: Russian air strikes in Syria Russian Deputy Defense Minister Anatoly Antonov speaks at a briefing in the Defense Ministry in Moscow, Russia. Antonov said the Russian air strikes in Syria have killed about 35,000 militants, including about 2,700 residents of Russia AP In pictures: Russian air strikes in Syria Jameel Mustafa Habboush, receives oxygen from civil defence volunteers, known as the white helmets, as they rescue him from under the rubble of a building following Russian air strikes on the rebel-held Fardous neighbourhood of the northern embattled Syrian city of Aleppo Getty In pictures: Russian air strikes in Syria Civil defence members rest amidst rubble in a site hit by what activists said were airstrikes carried out by the Russian air force in the town of Douma, eastern Ghouta in Damascus, Syria Reuters In pictures: Russian air strikes in Syria A girl carrying a baby inspects damage in a site hit by what activists said were airstrikes carried out by the Russian air force in the town of Douma, eastern Ghouta in Damascus, Syria Reuters In pictures: Russian air strikes in Syria Civilians and civil defence members look for survivors at a site damaged after Russian air strikes on the Syrian rebel-held city of Idlib, Syria Reuters In pictures: Russian air strikes in Syria Civilians and civil defence members carry an injured woman on a stretcher at a site damaged after Russian air strikes on the Syrian rebel-held city of Idlib, Syria Reuters In pictures: Russian air strikes in Syria Volunteers from Syria Civil Defence, also known as the White Helmets, help civilians after Russia carried out its first airstrikes in Syria In pictures: Russian air strikes in Syria The aftermath of Russian airstrike in Talbiseh, Syria In pictures: Russian air strikes in Syria Smoke billows from buildings in Talbiseh, in Homs province, western Syria, after airstrikes by Russian warplanes AP In pictures: Russian air strikes in Syria Russian Air Forces carry out an air strike in the ISIS controlled Al-Raqqah Governorate. Russia's KAB-500s bombs completely destroy the Liwa al-Haqq command unit In pictures: Russian air strikes in Syria Caspian Flotilla of the Russian Navy firing Kalibr cruise missiles against remote Isis targets in Syria Â© TASS/ITAR-TASS Photo/Corbis In pictures: Russian air strikes in Syria Russia claimed it hit eight Isis targets, including a "terrorist HQ and co-ordination centre" that was completely destroyed In pictures: Russian air strikes in Syria A video grab taken from the footage made available on the Russian Defence Ministry's official website, purporting to show an airstrike in Syria In pictures: Russian air strikes in Syria A release from the Russian defence ministry purportedly showing targets in Syria being hit In pictures: Russian air strikes in Syria Russia launched air strikes in war-torn Syria, its first military engagement outside the former Soviet Union since the occupation of Afghanistan in 1979. Russian warplanes carried out strikes in three Syrian provinces along with regime aircraft as Putin seeks to steal US President Barack Obama's thunder by pushing a rival plan to defeat Isis militants in Syria In pictures: Russian air strikes in Syria Caspian Flotilla of the Russian Navy firing Kalibr cruise missiles against remote Isis targets in Syria, a thousand kilometres away. The targets include ammunition factories, ammunition and fuel depots, command centres, and training camps Â© TASS/ITAR-TASS Photo/Corbis

Mr Putin has always maintained that his forces were engaged in Syria to battle Isis and other groups deemed to be terrorists. Syrian opposition activists and Western diplomats have long insisted that Moscow was instead focused on propping up ailing Syrian government forces. That claim was all but vindicated as Mr Putin said that his mission had “largely been accomplished” even though Isis still remains a major force in Syria, as does the al-Qaeda affiliate Jabhat al-Nusra.

Mr Putin insisted, however, that “Syria’s armed forces and the patriotic Syrian forces have been able to achieve a fundamental turnaround in the fight against international terrorism and have taken the initiative in almost in all respects.”

He said the Russian air campaign had allowed Mr Assad’s military to turn the tide of war and helped create conditions for peace talks. He said some troops would stay in the country to monitor the ceasefire and “create the conditions for the peace process”.