The Tartus naval base and Hmeimim air base are Russia's only military outposts outside the former Soviet Union and have been key to the Kremlin's activities in Africa and the Middle East.

Russian state media report that the Syrian opposition has "guaranteed" the security of the facilities, but it is not clear if Moscow will maintain control of them.

Here's what we know about them:

- Tartus -

The Tartus naval base on Syria's coast is Russia's only entrance point to the Mediterranean sea.

It is used as a refuelling and repair site for Russian vessels, allowing them to stay in the Mediterranean without having to return to Russia's Black Sea ports via the Turkish straits.

The site was leased to the Soviet Union in 1971 under a deal with Syria, becoming fully operational in 1977 as the Soviet co-operation with Arab states intensified during the Cold War.

It is a deep-water port, allowing it to host nuclear submarines.

With the Soviet collapse in 1991, many overseas military bases were closed but Tartus was kept open, albeit with a reduced presence.

Russia's military activity at the port ramped up during the Syrian civil war, which saw rebels mount an offensive against Assad.

In 2015, Russia launched a full-scale military intervention to keep Assad in power, carrying out devastating aerial bombardment of rebel-held areas.

The number of staff at the facility increased from "several people" to more than 1,700 by 2015, the Kommersant newspaper reported, although the number of troops there since Moscow launched its Ukraine offensive is not known.

Putin ordered the base's expansion in 2017, after Assad gave a 49-year lease on the facility free-of-charge in exchange for helping keep him in power.

The fate of the base since the lightning rebel offensive launched last month is unclear.

According to satellite images provided to AFP by Planet, none of the Russian warships based in Tartus were in port on December 9.

Russia's foreign minister Sergei Lavrov denied on Saturday that Russian ships were leaving the base.

- Hmeimim -

Russia built the Hmeimim airbase in Syria in 2015, repurposing an existing civilian airport near the port city of Latakia.

The base is believed to be well protected, with security perimeters and air defences that have a range of up to 250 kilometres (155 miles), according to Russian state media.

Moscow used the base to conduct air strikes on opposition-held areas throughout the Syrian civil war.

The Russian army does not publish information about its deployments. But many analysts believe the number of soldiers there drastically decreased after 2022, when Moscow began its military assault on Ukraine.

The base is also reported to have been a logistics hub and transit point for Russia's Wagner group, which conducts operations in Africa, a continent where the Kremlin is seeking to boost its influence.