At least nine people died when a car bomb exploded in the Syrian capital, a watchdog says, amid reports of battles raging around a major airport and a military airbase in the north of the country.
Many people were seriously wounded in the car-bomb attack in a northern Damascus neighbourhood, and the death toll may climb, the group's director Rami Abdel Rahmane told AFP on Friday.
The Syrian Observatory for Human Rights, which relies on a network of fighters and doctors to monitor the conflict in Syria, said the attack occurred in an area with a large population of Alawites, an offshoot of Shi'ite Islam and the minority community of President Bashar al-Assad.
State news agency SANA said the incident was a "terrorist attack" targeting a petrol station near a hospital.
Insurgents on Thursday besieged troops on the perimeter of Aleppo's international airport and around Taftanaz airbase in Idlib province, a day after the United Nations said 60,000 had died in the 21-month civil war.
The airport in Aleppo has been closed since Tuesday after repeated attacks by rebels, according to an airport official.
Hundreds of fighters from two hardline Islamist rebel groups, the Al-Nusra Front and Ahrar al-Sham, battled soldiers around the Taftanaz airbase, the Britain-based Observatory said as regime warplanes pounded rebel positions.
The rebels had remotely detonated a bomb at one of the base's gates the day before but were pushed back by the army, according to both the Observatory and a military source inside the airbase.
The military source told AFP that clashes outside Taftanaz had been non-stop for more than 48 hours and there had been a large number of rebel casualties.
Three rebels were also killed by troops around the Deir Ezzor military airport, as fighting broke out in the provincial capital in the east of the country.
In the town of Mleha, just east of Damascus, bodies were being recovered from a service station hit by a regime air strike on Wednesday.
The Observatory said at least 12 bodies were recovered, including several rebels. The Local Coordination Committees, a grassroots network of activists, estimated at least 50 people died in the attack.
The Observatory said 160 people were killed in violence across Syria on Thursday, including 72 civilians, almost half of whom were women and children.
Pakistan's UN ambassador Masood Khan meanwhile said international envoy Lakhdar Brahimi could meet with the United States and Russia next week to discuss ways to end the Syrian conflict.
Khan told reporters he had spoken to Brahimi on Wednesday and there was a new effort under way to find a political resolution.
"We are hoping there will be a trilateral meeting sometime next week between Moscow, Washington and Mr Brahimi," said Khan, whose country currently holds the rotating presidency of the United Nations Security Council.
On the humanitarian front, a 33-truck aid convoy organised by Turkish and Qatari relief groups left Istanbul on Thursday carrying 850 tonnes of flour.
"Assad's regime is bombing the bakeries and there is a very huge need for flour in Syria," said Huseyin Oruc, the vice-president of Turkey's IHH Humanitarian Relief Foundation.
The estimated death toll of 60,000 in the Syria conflict has unsettled observers.
UN High Commissioner for Human Rights Navi Pillay on Wednesday called it "truly shocking".
"Given there has been no let-up in the conflict since the end of November, we can assume that more than 60,000 people have been killed by the beginning of 2013," Pillay added.
The average number of deaths recorded in recent months was five times that registered by mid-2011, reflecting intensifying viciousness and the government's increased use of air strikes.
Pillay said "this massive loss of life could have been avoided" if the government of President Bashar al-Assad had not chosen the "ruthless suppression" of what initially were peaceful protests.
Karim Bitar, an analyst at the Institute for International and Strategic Relations, was sceptical the new toll would have a political impact.
"The world has become unfortunately so toughened to these figures, sort of anaesthetised. There is this terrible Stalin quote: 'One death is a tragedy; one million is a statistic'," he said.