President Vladimir Putin has ordered the partial withdrawal of Russian troops from Syria during a surprise visit to the war-torn country.

Russia first intervened in the conflict in 2015, staging air strikes in support of its ally.

It targeted both the Islamic State group and other jihadists, as well as rebels fighting government troops.

"I order the defence minister and the chief of general staff to start withdrawing the Russian group of troops to their permanent bases," Mr Putin said in a televised speech as he visited Russia's Hmeimim airbase in Syria.

"I have taken a decision: a significant part of the Russian troop contingent located in Syria is returning home to Russia."

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Mr Putin, who was welcomed by Syrian President Bashar al-Assad, said the troops had helped the Syrian army crush the "most battle-ready group of international terrorists," apparently referring to IS.

"Our homeland thanks you, my friends," Mr Putin said. "Have a safe trip. I thank you for your service."

Mr Putin and Mr Assad were pictured smiling and shaking hands.

Mr Putin made the stopover at the base in Latakia province, a regime stronghold, on his way to Egypt.

He said last month that efforts to end the war were entering a "new stage" as the focus shifted from military intervention to political reform.

More than 340,000 people have been killed since the conflict broke out in March 2011 with protests against Mr Assad's rule that sparked a brutal crackdown.