US President Barack Obama and Russia's President Vladimir Putin called Monday for an "immediate" end to the Syria conflict as 94 deaths were reported in a worsening artillery pounding of cities.
The call by the rival powers was made as Russia reportedly prepared to send two warships with marines to its naval base in Syria where UN monitors have suspended their patrols because of escalating violence.
"In order to stop the bloodshed in Syria, we call for an immediate cessation of all violence," the two leaders said in a statement after meeting on the sidelines of the Group of 20 summit in Los Cabos, Mexico.
"We are united in the belief that the Syrian people should have the opportunity to independently and democratically choose their own future," the leaders said.
Putin told reporters that he and Obama had found "many common points" on the 15-month-old uprising against President Bashar al-Assad.
Obama said he and Putin agreed on the need for a "political process" to halt the conflict and had pledged to work with UN-Arab League envoy Kofi Annan on the crisis.
But there was little sign they had agreed a way to end the conflict which monitors say has now cost more than 14,400 lives.
The United States has voiced frustration at Russia's blocking of UN Security Council moves against Assad. The head of the UN mission in Syria is to brief the Security Council on Tuesday on the deteriorating conflict.
The United States, Britain and France are working on a new UN Council resolution in which they want to threaten sanctions against Assad. But Russia, Syria's main international ally, and China have already blocked two resolutions which just hinted at measures.
A British marine insurer, meanwhile, said it had cancelled cover for a Russian ship, the MV Alaed, following reports it was carrying Mi-25 helicopter gunships destined for Syria.
"We have already informed the ship owner that their insurance cover ceased automatically in view of the nature of the voyage," Standard Club said.
The Daily Telegraph reported that the ship was stopped off the coast of Scotland.
Moscow news reports, meanwhile, said Russia is preparing to send two amphibious assault ships and marines to the Syrian port of Tartus where Russia has a naval base to ensure the safety of its nationals.
The amphibious warships, The Nikolai Filchenkov and The Tsezar Kunikov, are to be sent to Tartus with a "large" group of marines, Interfax news agency quoted an officer at Russian naval headquarters as saying.
There was no official confirmation of the report by Russian authorities, however.
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The Tsezar Kunikov can carry 150 troops and armaments including tanks, while The Nikolai Filchenkov can carry up to 1,500 tonnes of cargo and equipment, the report said.
Interfax said the ships could be used to evacuate Russian nationals.
Syrian government forces, meanwhile, pounded rebel strongholds in the central city of Homs and Damascus.
The Syrian Observatory for Human Rights said 94 people were killed across the country on Monday, including 63 civilians, three army deserters and 28 government troops.
Government troops stepped up a siege of Tasas in the southern province of Daraa, cradle of the anti-regime revolt, said the rebel Free Syrian Army.
The army broke into the south of Tasas and launched raids, said FSA spokesman Louay Rashdan.
One blast at Mohassan in the eastern province of Deir Ezzor killed seven people, including two rebel commanders, the Syrian Observatory said.
Clashes and shelling persisted in several areas of Damascus province, including the towns of Douma and Qudsaya which have been under bombardment for the past five days.
An activist who identified himself as Mahmoud Doumani told AFP there was widespread destruction in Douma.
"Regime forces have destroyed homes, farms and many mosques over the past week. But in the past couple of days, in the absence of the UN monitors, attacks on Douma have become even worse than before," Doumani said, adding that families who have not fled the town are in hiding.
The 300 unarmed monitors in the UN observer mission suspended operations on Saturday because of the heightened violence.
The mission's leader Major General Robert Mood has urged the government and opposition to let "women, children, the elderly and the injured to leave conflict zones". But so far there has been no letup.
Mood is to brief the Security Council on Tuesday amid growing doubts among western nations that the observers will be allowed to stay in the country.
"I think there will be a lot of member states of the council, including us, who will be questioning now what the future is for the mission and, therefore, by extension the Annan plan," said Britain's UN ambassador Mark Lyall Grant.
UN rights chief Navi Pillay demanded a halt to the government bombardment of populated areas. "Such actions amount to crimes against humanity and possible war crimes," Pillay told the UN Human Rights Council.