Russia is poised to send two navy ships to Syria to protect Russian citizens and its naval base there, Interfax news agency reported.

One vessel can carry up to 150 landing troops and tanks. Both ships are heading to the Syrian port of Tartus. It is unclear when they will get there.

"The crews of the Nikolai Filchenkov and the Tsezar Kunikov and SB-15 rescue tug together with marines on board are able to ensure the security of Russian nationals and evacuate part of the property of the logistical support base if need be," an unnamed Russian official told Interfax.

One of the few countries to support Assad's regime, Russia has blocked any international effort to put in place sanctions against the country and has been accused of providing arms to government forces.

There was no official confirmation of the latest deployment from the navy or the defence minister.

UN Secretary of State Hillary Clinton condemned Russia for fuelling the violence by sending helicopters to Syria, a move she warned would "would escalate the conflict quite dramatically".

Russia hit back saying it was not making any new deliveries and had only carried out repairs of helicopters sent years ago.

The move to send ships has increased suspicions in the West that Syria is still aiding the regime.

"Russia is obviously concerned about Islamic regimes and perhaps most important of all it is terrified of chaos," Mark Galeotti, who chairs the Centre for Global Affairs at New York University, wrote in the Independent Online.

"Russia feels that the West doesn't know how to handle regime change and that the outcome is almost invariably the kind of chaos from which Islamic extremist movements arise."

The White House again urged Syria to stick to commitments it has made in recent months, including the ceasefire.

"We are consulting our international partners regarding next steps toward a Syrian-led political transition" said Washington. "The sooner this transition takes place, the greater the chance of averting a lengthy and bloody civil war."

Opposition activists have claimed that the government has intensified its shelling of rebel strongholds in Homs.

The UN has withdrawn its observers due to worsening security conditions.