Syrian activists and witnesses say the army is shelling residential areas in the central city of Homs as the government moves to crush a popular nationwide revolt.
The besieged city has seen some of the largest anti-government demonstrations in recent days.
A witness reported hearing loud explosions and automatic gunfire throughout the night and early Wednesday, adding residential areas were being shelled.
Activists confirmed the report. All spoke on condition of anonymity for fear of reprisals.
They say security forces opened fire opened fire on anti-government protesters in southern Syria Tuesday night, killing at least three people.
Rights groups say more than 750 people have been killed in the crackdown that began in mid-March.