More than 60,000 people have been killed in Syria since the uprising against President Bashar al-Assad's regime erupted in March 2011, a top UN official said.

Navi Pillay, the UN High Commissioner for Human Rights, said that an exhaustive analysis carried out by data specialists showed that 59,648 people had died through the end of November.

Speaking to Al Jazeera, Rupert Colville, spokesman for Pillay, said the death toll could be much higher.

"What we have done is take the statistical analysis of seven of the lists of casualties that exist, analyse them all and remove all the double counting," he said.

"But the criteria are quite strict. There has to be a set amount of information and there may well be people who have been killed who aren't included as a result of that."

He said the 60,000 figure should be treated as an indicative number and not a real number.