Russian President Vladimir Putin has signed a law ratifying an agreement enabling Russia to expand operations at its naval facility in the Syrian port of Tartus.
The document was posted on the official website for Russian legislation after Putin signed it on December 29.
It could help cement what Putin has said would be a "permanent" Russian presence at the Tartus facility and the Hmeimim air base, key platforms for Russia's campaign backing Syria's government in the nearly seven-year war in the Middle Eastern country.
The agreement, signed in Damascus in January 2017, allows for the Russian Navy to expand the technical support and logistics facility at Tartus, which is Moscow's only naval foothold in the Mediterranean.
It allows Russia to keep up to 11 warships, including nuclear-powered vessels, at Tartus at any time for the next 49 years. The deal is to be prolonged automatically for 25-year periods upon its expiration.
It also allows Russian ships to enter Syria's territorial waters, internal waters, and ports, to use the Tartus facility free of charge.
The agreement also provides Russian military personnel at the facility with immunity and regulates the status of the military personnel and members of their families there.
Russia has given President Bashar al-Assad's government crucial support throughout the war, which has killed hundreds of thousands of people and driven millions from their homes since it began with a crackdown on pro-democracy protests in 2011.
Moscow helped Assad avoid possible defeat by starting a campaign of air strikes in September 2015, in many cases using Hmeimim as a base. It has also launched strikes from warships in the Mediterranean.
During a visit to the air base on December 11, Putin declared victory over "the most combat-capable international terrorist group" -- a reference to the extremist group Islamic State (IS) -- and announced a partial withdrawal of Russian troops.
Western officials say that the Russian campaign, particularly in its earlier stages, has focused heavily on targeting rebels seeking Assad's ouster rather than IS militants.
Putin said on December 28 that more than 48,000 Russian military personnel have served in the operation in Syria, and that the facilities at Hmeimim and Tartus would continue to operate "on a permanent basis."
With IS in retreat and diplomats pressing ahead with efforts to forge a political solution, analysts say Russia is eager to make its position in Syria as strong as possible in order to wield influence on future developments.