Forces loyal to President Bashar al-Assad shelled rebel-held areas across Syria on Sunday as fierce clashes were reported in second city Aleppo where a fire tore through a medieval souk.
The fighting in Aleppo city was accompanied by intense overnight shelling that continued into the morning, destroying houses and killing at least three people including two civilians, said the Syrian Observatory for Human Rights.
Aleppo, Syria's most populous city, has been the main battleground for the past two months of the country's 18-month conflict, and has been gripped by fighting on an unprecedented scale in recent days.
Much of the violence has centred in and around the Old City, and this is believed to have sparked the fire in the centuries-old souk marketplace which destroyed many shops, said an AFP correspondent and the Observatory.
Clashes were reported elsewhere in the northern province of Aleppo, where rebel mortar fire damaged two helicopters at the Al-Nairab military airport, said the group which relies on a network of activists on the ground.
In Damascus province, rebels killed nine soldiers when they attacked a military checkpoint on the road linking the capital with Qatana to the southwest, the Britain-based Observatory reported.
That came after soldiers backed by aerial firepower stormed the rebel stronghold of Harasta as regime forces carried out arrest raids in the town of Zabadani, said the Syrian Observatory for Human Rights.
Elsewhere, troops trying to dislodge rebels fired heavy artillery into areas of the southern province of Daraa, central region of Hama and Idlib in the country's northwest, said the Observatory.
In the northeastern province of Hasakeh, the army fired on several houses, injuring several people, as security forces conducted arrest operations in the coastal city of Banias, it added.