Russia has begun withdrawing some of its troops from Syria, Defence Minister Sergei Shoigu said on Monday.
President Vladimir Putin ordered the partial withdrawal during an unannounced visit to Syria on Monday.
Russian support has been crucial in turning the tide of Syria's civil war in favour of government forces, led by president Bashar al-Assad.
Mr Putin made a similar withdrawal announcement last year, but Russian military operations continued.
When asked how long it would take for Russia to withdraw its military contingent, Mr Shoigu said that this would "depend on the situation" in Syria.
The Russian president was met by Mr al-Assad at the Russian Hmeimim airbase near Latakia.
Mr Putin said that if "terrorists raise their heads again", Russia would "carry out such strikes on them which they have never seen".
He told President Assad that Russia wanted to work with Iran, the government's other key ally, and Turkey, which backs the opposition, to help bring peace to Syria.
The Syrian and Russian air forces carried out daily air strikes on the rebel-held east of the city before it fell in December 2016, killing hundreds of people and destroying hospitals, schools and markets, according to UN human rights investigators, reports BBC..