BEIRUT: Warplanes bombarded rebel positions across strife-torn Syria on Thursday, activists said, while fierce clashes raged near the ancient citadel in the central city of Homs.

Fighter jets rained bombs on targets in the southern province of Daraa, on Homs and Hama in the centre, Raqa in the north and Idlib in the northwest, said the Syrian Observatory for Human Rights.

Rebels meanwhile assaulted a checkpoint near the army-held citadel in the heart of Homs city, killing eight soldiers, the Britain-based Observatory said.

A number of neighbourhoods of Homs been devastated by nine months of a suffocating military siege and an escalated week-long campaign to crush the insurgency there.

Also in Homs, fighting raged for the sixth consecutive day over the symbolic district of Baba Amr, which rebels infiltrated at the weekend in a surprise counter-offensive on an area captured a year ago by the army.

The air force has escalated its use of fighter jets as rebels seize more and more territory across Syria.

Thursday's violence comes a day after at least 159 people were killed across the country, among them 63 civilians.

The conflict in Syria has left some 70,000 people dead in the past two years, the UN says, and has forced more than one million people to flee the country.

The conflict broke out after regime forces unleashed a brutal crackdown against a peaceful uprising that erupted on March 15, 2011. The uprising later morphed into a bloody insurgency.