UN High Commissioner for Human Rights Navi Pillay made the announcement in a statement issued in Geneva on Wednesday.
"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," she stated.
Pillay also noted that 59,648 people had died by the end of November 2012 in the unrest.
“The number of casualties is much higher than we expected, and is truly shocking… Although this is the most detailed and wide-ranging analysis of casualty figures so far, this is by no means a definitive figure.”
Earlier in the day, at least 30 people were killed in an air raid on a gas station in al-Maliha, a suburb of the capital Damascus.
Many other people were also injured in the attack.
Opposition activists accused the Syrian forces of carrying out the attack, but the government has not released any official statement on the raid.
Many people, including large numbers of security forces, have been killed in the turmoil that began in Syria in March 2011.
The Syrian government says that the chaos is being orchestrated from outside the country, and there are reports that a very large number of the armed militants are foreign nationals.
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