Russia is preparing to withdraw personnel from its naval maintenance and supply facility on Syria's Mediterranean coast, Interfax news agency reported on Wednesday.

If accurate, the plan would reflect safety concerns as the United States and its allies gear up for a probable strike to punish President Bashar Al-Assad for an alleged gas attack his foes say killed hundreds of people.

The modestly staffed and equipped facility in the port of Tartous is Russia's sole military base outside the former Soviet Union, serving as a foothold in Syria and helping it keep warships travelling through the Eastern Mediterranean supplied.

Citing an unnamed source in the Russian navy headquarters, Interfax reported that the facility's personnel had boarded the repair vessel stationed there and that Russian warships would escort it out.

The report did not say when the vessel would leave Tartous or how many people were aboard. The Defence Ministry declined to comment, saying questions should be addressed to the navy. Navy officials could not immediately be reached for comment.

Following Russian media reports in June that military personnel had been withdrawn from the facility, the Defence Ministry said nobody had left. It said personnel there were civilians.

The ministry gave no figures, but military analysts have said the facility is staffed by about 100 technicians who service Russian ships that call for supplies and minor repairs.

Russian officials say there are tens of thousands of Russian citizens in Syria, many of them women married to Syrians and their children.

Russia's Emergency Situations Ministry said late on Tuesday it had evacuated 89 people who wanted to leave Syria, including 75 Russian citizens, on a flight from Latakia to Moscow. It said the ministry has flown 730 people out of Syria this year.

Russia has been Assad's most powerful backer in a conflict that has killed more than 100,000 people since 2011, supplying what it says are defensive weapons and blocking UN Security Council resolutions to condemn him or threaten sanctions.

Moscow has strongly urged the United States and other nations not to attack Syria, saying the use of force without a UN mandate would violate international law, but has also said it has no plans to be drawn into a military conflict. - Reuters