Syrian government troops regained control of a historic mosque in Aleppo after pushing rebel troops back from the area, a human rights group reported Sunday.

The London-based Syrian Observatory for Human Rights said that government troops recaptured the mosque from rebels after "intense clashes" nearby and in several other neighborhoods, some of which were damaged by government artillery.

The Syrian opposition had reported the 12th-century Umayyad Mosque was set afire during heavy fighting Saturday, with one opposition activist accusing government troops of setting the building ablaze. The head of the U.N. cultural agency UNESCO had urged all parties to protect the mosque, warning it was "severely endangered" by the battle for Syria's commercial capital.

Syria's state-run news agency said government troops had killed numerous "terrorists" around the city during Sunday's fighting and defused a truck bomb that had been loaded with 3 tons of explosives near a major intersection.

Aleppo is a UNESCO World Heritage Site, dominated by an ancient citadel. Portions of its medieval marketplace burned in September, about a month into the battle for the city.

Opposition reports 220 deaths

Opposition activists from the Local Coordination Committees of Syria reported 220 new deaths in the grinding conflict on Sunday, including an estimated 100 left at a state hospital outside Damascus.

Video of the scene distributed online showed the bodies piled into what appeared to be a refrigerated truck outside the hospital in Mouadamiyeh, in the Damascus suburbs. Alexia Jade, an opposition activist in Damascus, told CNN that many of the bodies were found with their hands tied behind their backs and showed signs of torture.

The remains were quickly removed by members of a pro-government militia, she said.

CNN could not independently confirm the authenticity of the video.

The LCC also reported heavy fighting in the capital's suburbs throughout the day, as well as around Idlib, Latakia, Homs and Deir Ezzor.

An estimated 30,000 people have been killed since March 2011, when anti-government protesters took to the streets calling for political reform. Syrian President Bashar al-Assad responded with a clampdown that spawned an armed conflict.

CNN cannot independently confirm reports of fighting or casualty counts in Syria because the government has restricted access to international journalists.

Government, rebels swap prisoners

The Syrian Observatory reported what is believed to be the first government-sanctioned exchange of prisoners in the conflict Sunday, with rebel fighters trading the son of a Syrian government official for two prisoners who had been sentenced to death, the rights group said.

Rami Abdul Rahman, a spokesman for the group, told CNN that the exchange was witnessed by a lawyer and is the first prisoner swap approved by al-Assad.

A member of a rebel military unit who took part in the exchange, identified as "Abu Ahmad," said the rebels initially demanded the release of 20 prisoners in exchange for the son of Ali Shuaibi, identified as a negotiator for al-Assad's government. After the government eliminated "one name after another," the rebels proposed the two condemned men, and the government agreed.

The talks lasted over 10 days. Abu Ahmad said the opposition prisoners were given "severe beatings" before their release, and government forces conducted intensive airstrikes in the area following the exchange.

U.N. envoy holds talks in Turkey, Iran

As the fighting continued, the diplomat tasked with finding a peaceful end to the conflict held talks with officials in Turkey and Iran.