Russia sent warships to the Mediterranean to prepare a potential evacuation of its citizens from Syria, a Russian news agency said on Tuesday, a sign President Bashar al-Assad's key ally is worried about rebel advances that now threaten even the capital.

Moscow acted a day after insurgents waging a 21-month-old uprising obtained a possible springboard for a thrust into Damascus by seizing the Yarmouk Palestinian camp just 2 miles from the heart of the city, activists said.

The anti-Assad opposition has posted significant military and diplomatic gains in recent weeks, capturing a series of army installations across Syria and securing formal recognition from Western and Arab states for its new coalition.