At least 45 people were killed in an overnight attack by Syrian government forces on protesters in the eastern city of Hama, local media reported, quoting witnesses and rights activists.
At least 40 people were killed when troops loyal to embattled President Bashar al-Assad opened fire from machine guns in Hama's northern suburb. Another five people, including two children, were killed by a tank mortar while trying to leave the city in their car.
The city, which has been a scene of fierce clashes between al-Assad supporters and opponents for the past several days, has been cordoned off by government troops, with tanks and armored vehicles deployed in the city center, reports said. The city's electricity, water and phone lines have been cut.
The attack on Hama came as al-Assad signed a decree on Thursday authorizing a multiparty system in Syria. In line with the new law, other political parties besides Baath, in power since 1963, are allowed to be created in Syria.
The attack also came hours after the United Nations stepped up pressure on the Syrian government, condemning "the widespread violations of human rights and the use of force against civilians by the Syrian authorities" in a UN Security Council presidential statement.
The condemnation followed a series of deadly attacks on protesters by government troops, which left some 140 dead since Sunday's crackdown on Hama, according to rights activists.