Syrian ground and air forces bombarded rebel strongholds on the outskirts of Damascus and other areas around the country Friday while anti-government forces targeted a military post near the capital with a car bomb, activists said.

The Britain-based Syrian Observatory for Human Rights said warplanes targeted neighborhoods around the capital including Douma, which troops have been trying to recapture for weeks. Two air raids there Thursday killed 12 people and caused heavy damage.

The Observatory added that a car bomb blew up outside a military intelligence building in the northern Damascus suburb of Nabk but had no immediate word on casualties.

An amateur video posted online showed a strong explosion with black smoke billowing from Nabk and the narrator said the blast targeted the military intelligence facility. The video appeared genuine and corresponded to other AP reporting on the events depicted.

The violence came two days after the U.N. said that more than 60,000 people have been killed since Syria's crisis began in March 2011 — a figure much higher than previous opposition estimates.

Damascus-based activist Maath al-Shami said government troops were firing rockets and mortars from the Qasioun mountains overlooking the capital down at orchards near the southern suburbs of Daraya and Kfar Sousseh. The Observatory says troops were also fighting rebels in Aqraba and Beit Saham, also south of Damascus, near the capital's international airport.

The army command said in a statement Thursday night that troops carried out operations in suburbs of the capital including Douma and Daraya.

"Regime forces are facing very strong resistance in Daraya," said al-Shami via Skype, but said that government forces had been able to advance down the main street in the suburb.

The government capture of Daraya would provide a boost to the regime's defense of Damascus. It is close to a military air base as well as the government's headquarters and one of President Bashar Assad's palaces.

In the north, rebels resumed a week-old offensive against regime-held airbases. The government's air power poses the biggest obstacle to advances by opposition fighters.

Activists said there were battles around the military air base of Taftanaz in the northern province of Idlib close to the Turkish border and near the international airport of Aleppo, Syria's largest city and commercial center.

Fadi al-Yassin, an activist based in Idlib, said the rebels killed on Thursday the commander of Taftanaz air base, a brigadier general.

"The battles now are at the gates of the airport," al-Yassin said via Skype. He added that it has become very difficult for the regime helicopters to take off and land at the base.

He said warplanes taking off from airfields in the central province of Hama and the coastal region of Latakia are participating in attacking rebels around Taftanaz.

The Syrian Army General Command said troops directed "painful strikes" against the "armed terrorist groups" of Jabhat al-Nusra, a group the U.S. claims is linked to al-Qaida-linked organization. The Syrian military says the extremist group is carrying out the Taftanaz attack, and that dozens of fighters were killed.

Aleppo airport has been closed since Monday. A government official in Damascus said the situation is relatively quiet around the facility, adding that it is up to civil aviation authorities to resume flights.

A man who answered the telephone at the information office at the Damascus International Airport said, "God willing, flights will resume to Aleppo very soon."

Syrian rebels are fighting a 21-month-old revolt against the Assad regime. The crisis began with pro-democracy protests but has morphed into a civil war.