Syrians will have to cope with a full-scale civil war alone, Konstantin Kosachyov, deputy chairman of Russia's upper house of parliament said on Sunday, the Interfax news agency reported.

Syrian rebels announced on state television on Sunday that they had ousted President Bashar al-Assad, eliminating a 50-year family dynasty in a lightning offensive that raises the spectre of a new wave of instability in a Middle East gripped by war.

Russia, a staunch Assad ally, intervened decisively in 2015 to prop him up during Syria's civil war, which began in 2011.

Russian war bloggers have raised fears about the fate of two strategically-important Russian military facilities in Syria.