Russia despatched a flotilla of warships to its naval base in the Syrian port of Tartus on Tuesday in an apparent show of support for President Bashar al-Assad.
Two destroyers and three amphibious landing vessels carrying marines set sail from Russian bases in the Arctic and the Black Sea, according to Russian military sources.
Russia’s defence ministry insisted that the mission was part of a previously scheduled exercise in the Atlantic, Mediterranean and Black Sea and at least one of the vessels in the flotilla has patrolled waters off Syria earlier this year.
But Western diplomats say the purpose of the mission is to show tangible support for Mr Assad, to warn the West against military intervention in Syria and to prepare for the possible evacuation of Russian nationals from the country.
Russia renewed naval patrols in the Mediterranean in 2007 – after a 15-year hiatus – with a wider aim of expressing the country’s military resurgence.
It was unclear whether the ships were carrying weapons supplies or large numbers of marines.
This week, Moscow announced that it would halt the delivery of new weapons to the Syrian armed forces, while some of Mr Assad’s leading opponents have been invited to the Kremlin for talks.
Meanwhile, Kofi Annan, the UN and Arab League special envoy to Syria, sought regional support for his faltering peace plan as he held talks with senior officials in both Iran and Iraq.
Mr Annan, who said this week that he was working on a new proposal to end the fighting in Syria, said he believed that Iran could play a “positive role” in ending the crisis, despite its close relationship with the Assad regime.
The United States has accused Iran of propping up Mr Assad, by giving him arms and logistical support.
Mr Annan has said that he will brief the Syrian opposition on a new approach he has agreed with Mr Assad earlier this week. Although he would not be drawn on the specifics of the proposal, he said that his new plan involved ending the conflict on a step-by-step basis, beginning with districts that have suffered the worst violence.