The Local Coordination Committees activist group said Homs was under “brutal shelling” on Tuesday.

Syrian forces have been shelling the city for more than a week. The latest onslaught began last Saturday to retake parts of the city captured by rebel forces.

With diplomatic efforts bogged down, the conflict is taking on the dimensions of a civil war, with army defectors clashing almost daily with soldiers.

UN human rights chief Navi Pillay warned on Monday that the Security Council’s failure to take action has emboldened the Syrian government to launch an all-out assault.