Syrian President Bashar al-Assad's forces mounted a series of attacks in Damascus and other areas of Syria on Saturday to crush the rebels who killed four key members of the president's inner circle, opposition activists reported.
Explosions were heard in the district of al-Midan in southern Damascus, believed to be caused by shells fired by pro-regime forces hunting for rebels, according to the opposition Syrian Observatory for Human Rights, DPA reported.
Sounds of gunfire were heard in the same district which, according to state media, military forces had recaptured from rebels after a crackdown on Friday.
Al-Assad's forces, meanwhile, bombarded the area of Housh Arab on the outskirts of the capital, causing unspecified casualties, the London-based organization said.
Fierce fighting entered its seventh day in Damascus, between the government forces and rebels who claimed responsibility for a bomb attack on Wednesday that killed the defence minister and three other aides to al-Assad, including his brother-in-law.
The rebel Free Syrian Army this week launched what it called a "Damascus volcano" offensive to gain control of the city.
Beyond Damascus, clashes were reported between the military and rebels in the town of al-Qusair in the central province of Homs, a key opposition stronghold.
The regime forces were heavily shelling the pro-opposition town of Talbisa in Homs, said the opposition.
A similar bombardment by government forces targeted the province of Aleppo, followed by clashes with rebels in its centre, said activists.
The fighting forced the closure of shops, they added. No specific casualty figure was reported.
In Daraa, the cradle of the revolt against al-Assad's regime, clashes killed four army soldiers and two rebel fighters, said the Syrian Observatory for Human Rights.
The surge in violence comes a day after the United Nations Security Council voted unanimously to extend an observers' mission by a final 30 days.
The team's mandate was extended with the understanding that the observers would assist a transition in Damascus or pull out if no political solution is found to end the 17-month conflict.
The 300-strong mission was dispatched to Syria in April to monitor a UN-brokered truce, but suspended its activities last month because of what its chief called "unprecedented levels" of violence.
In Istanbul meanwhile, a leading figure in the Syrian Muslim Brotherhood declared that the peace plan of UN-Arab League mediator Kofi Annan had failed.
"We accepted the Annan plan at the beginning with the hope that it would stop the massacre of civilians. However, international steps taken have only led to Assad's gaining time," Gaysa Ulabi told Turkish news agency Anadolu.
The six-point plan on Syria is based on a ceasefire that never held.
"The Syrian people are in great solidarity within themselves. Despite Assad's plans to create enmity between sects and ethnic groups, the Syrian people have united as one," said Ulabi.
Al-Assad did not show up on Friday for a funeral of his aides who were killed in Wednesday's attack, fuelling speculation about his whereabouts.
The attack at a national security building in Damascus was seen as a severe blow to al-Assad's rule.