* U.N. human rights chief calls new toll "truly shocking"
* Air strike on petrol station kills at least 30 -activists
* Rebels renew assault on air base in north
By Khaled Yacoub Oweis and Tom Miles
AMMAN/GENEVA, Jan 2 (Reuters) - More than 60,000 people have died in Syria's uprising and civil war, the United Nations said on Wednesday, dramatically raising the death toll in a struggle that shows no sign of ending.
In the latest violence, dozens were killed in a rebellious Damascus suburb when a government air strike turned a petrol station into an inferno, incinerating drivers who had rushed there for a rare chance to fill their tanks, activists said.
"I counted at least 30 bodies. They were either burnt or dismembered," said Abu Saeed, an activist who arrived in the area an hour after the 1 p.m. (1100 GMT) raid in Muleiha, a suburb on the eastern edge of the capital.
In the north, rebels launched a major attack to take a military airport, and said they had succeeded in destroying a fighter plane and a helicopter on the ground.
U.N. Human Rights Commissioner Navi Pillay said in Geneva that researchers cross-referencing seven sources over five months of analysis had listed 59,648 people killed in Syria between March 15, 2011 and Nov. 30, 2012.
"The number of casualties is much higher than we expected and is truly shocking," she said. "Given that 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."
There was no breakdown by ethnicity or information about whether the dead were rebels, soldiers or civilians. There was also no estimate of an upper limit of the possible toll.
Previously, the opposition-linked Syrian Observatory for Human Rights monitoring group had put the toll at around 45,000 confirmed dead but said the real number was likely to be higher.
Video footage taken by activists at the scene of the air strike on the petrol station showed the body of a man in a helmet still perched on a motorcycle amid flames engulfing the scene. Another man was shown carrying a dismembered body.
The video could not be verified. The government bars access to the Damascus area to most international media.
The activists said rockets were fired from a nearby government air base at the petrol station and a residential area after the air raid.
"Until the raid, Muleiha was quiet. We have been without petrol for four days and people from the town and the countryside rushed to the station when a state consignment came in," Abu Fouad, another activist at the scene, said by phone.
President Bashar al-Assad's forces also fired artillery and mortars at the capital's rebellious districts of Douma, Irbin and Zamlaka, activists living there said.
After nightfall there was shelling in the Jobar and Assali districts, and fighting occurred in the northern suburb of Harasta, on the highway leading north, Syria's main artery.
Assad's forces control the centre of the capital, while rebels and their sympathisers hold a ring of southern and eastern suburbs that are often hit from the air.
The Observatory said a separate air strike killed 12 members of a family, most of them children, in Moadamiyeh, a southwestern district near the centre of Damascus where rebels have fought for a foothold.
The rebels hold wide swathes of the north and east of the country, but have been unable to protect the areas they control from Assad's air power. Their main targets in recent months have been air bases, with a goal of preventing the government from using its jets and helicopters.
The rebels launched a major attack on Wednesday on Taftanaz, a northern air base which they hope to seize. A statement by the northern rebel Idlib Coordination Committee said they had battled their way to the airport's main command building but were not yet in control of the site.
The statement said the rebels had detonated a car bomb inside the Taftanaz airport grounds and destroyed a helicopter.
A rebel speaking from near the airport told Reuters the base's main sections were still in loyalist hands but rebels had destroyed a fighter jet as well as the helicopter.
The family of an American freelance journalist, James Foley, 39, said on Wednesday he had been missing in Syria since being kidnapped six weeks ago by gunmen. No group has publicly claimed responsibility for his abduction.
Syria was by far the most dangerous country for journalists in 2012, with 28 killed there.
The conflict began in March 2011 with peaceful protests against four decades of Assad family rule and turned into an armed revolt after months of government repression.
Both sides have been accused of committing atrocities in the 21-month-old conflict, but the United Nations says the government and its allies have been more culpable.
In the latest evidence of atrocities, Internet video posted by Syrian rebels shows armed men, apparently fighters loyal to Assad, stabbing two men to death and stoning them with concrete blocks in a summary execution lasting several minutes.
Reuters could not verify the provenance of the footage or the identity of the perpetrators and their victims. The video was posted on Tuesday but it was not clear where or when it was filmed. However it does clearly show a summary execution and torture, apparently being carried out by government supporters.
At one point, one of the assailants says: "For God's eyes and your Lord, O Bashar," an Arabic incantation suggesting actions being carried out in the leader's name.
The video was posted on YouTube by the media office of the Damascus-based rebel First Brigade, which said it had been taken from a captured member of the shabbiha pro-government militia.
The perpetrators show off for the camera, smiling for close-up shots, slicing at the victims' backs, then stabbing them and bashing them with large slabs of masonry.
Syria's civil war is the longest and deadliest conflict to emerge from uprisings that began sweeping the Arab world in 2011 and has developed a significant sectarian element.
Rebels, mostly from the Sunni Muslim majority, confront Assad's army and security forces, dominated by his Shi'ite-derived Alawite sect, which, along with some other minorities, fears revenge if he falls.