Syria's uprising has claimed the lives of at least 60,000 people, according to a comprehensive UN study, significantly raising the estimated death toll and adding to pressure on world powers to stop the bloodshed. Following what it described as "an exhaustive analysis carried out by data specialists" using seven different sources, the UN human rights office compiled a list of 59,648 people killed since the start of the initially peaceful uprising against President Bashar al-Assad in March 2011 until the end of November 2012. Entries that did not give the victim's full name and the date and location of their death were excluded. "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," said Navi Pillay, UN human rights commissioner. Opposition activists had previously said that about 45,000 people had been killed. The rate of killing has gathered pace as the uprising has turned into a civil war involving fighter jets, helicopter gunships and car bombs. In the summer of 2011, there were about 1,000 deaths per month, but since July 2012 this had risen to an average of more than 5,000, the UN said. Such sobering figures from an independent body, released days after Lakhdar Brahimi, the international envoy, warned that the death toll could hit 100,000 in 2013, are likely to increase pressure on international powers to bring an end to the conflict. "The failure of the international community, in particular the Security Council, to take concrete actions to stop the bloodletting, shames us all," said Ms Pillay. But recent hopes of progress on an internationally mediated transition agreement in Syria received a setback at the end of the year when Russia, a longtime ally of the regime, said there was "no possibility" of persuading Mr Assad to leave. An internationally recognised coalition of opposition groups also rebuffed an invitation to talks in Moscow, restating its insistence that Mr Assad's departure was a precondition for negotiations. The lethal nature of the conflict was underscored on Wednesday when an air strike on a petrol station in the Damascus suburbs killed at least 10 and perhaps dozens of people, many of whom were thought to be queuing for fuel according to activists. Acute fuel shortages often force people to waiting for hours to get petrol in Syria. Grim amateur video apparently taken at the scene shortly afterwards showed incinerated and in one case dismembered bodies amid the burnt-out vehicles and still raging flames. According to the Syrian Observatory for Human Rights, a pro-opposition monitoring group based in the UK, some of the dead were rebels. On Wednesday, there was also fierce fighting in the northern province of Idlib, where rebels are trying to gain control of a military air base in Taftanaz. The family of a freelance American journalist reporting in Syria meanwhile announced that he had been abducted more than a month ago and pleaded for his release. It is not clear whether 39-year-old James Foley was taken by a pro or anti-government group.