Government forces continued to bombard the central Syrian city of Homs on Monday with mortars and artillery fire. It was the third day of a relentless assault by Syrian forces.
The government denied shelling the city, insisting instead that "armed terrorist groups" were attacking civilians and police in several areas.
Several neighborhoods in Homs are under the control of the rebels. Many refer to the city as "the capital of the Syrian revolution."
So far, more than 250 people have been killed in what's being called the deadliest incident since the uprising began 11 months ago.
Human rights groups claimed government forces also bombed a makeshift hospital, causing even more casualties.
The Syrian government has blocked all independent reporting from the troubled area, making it impossible to verify accounts from both sides.
Meanwhile, the United Nations Security Council held a rare weekend session to try to pass a resolution calling for Syrian President Bashar al-Assad to step down.
China and Russia vetoed the plan, defeating the resolution's passage. The U.S. ambassador to the U.N. condemned the double veto.
"Mr. President, the United States is disgusted that a couple of members of this council continue to prevent us from fulfilling our sole purpose here, addressing an ever-deepening increasing crisis in Syria and a growing threat to regional peace and security," U.S. Ambassador Susan Rice said.
"Any further bloodshed that flows will be on their hands," she added.