Dozens of civilians in the Syrian city of Homs were killed in cold blood, the government and opposition said yesterday, disputing responsibility for what both sides called a massacre during a visit from UN-Arab League special envoy Kofi Annan.

Syrian forces unleashed a barrage of artillery on the battered city of Homs for hours before dawn today, killing more than 200 people in what appeared to be the bloodiest episode in the 11-month-old uprising, activists said.