Rebels seized control of the historic Umayyad Mosque in Syria's second city of Aleppo on Thursday after several days of fierce clashes that damaged the building, a watchdog reported.
State news agency SANA, meanwhile, said a car bomb exploded in a regime-held suburb of the central city of Homs, killing one person and wounding 24 others.
In Aleppo, regime troops were forced to withdraw from the mosque at dawn, taking up positions in buildings around the landmark structure, said the Syrian Observatory for Human Rights.
The mosque's museum caught fire during the battle, causing its ceiling to collapse, adding to damage done in October when one of its intricately sculpted colonnades was charred in clashes.
Aleppo's director of Islamic endowments said the mosque's library, which contains "valuable Islamic relics and Koranic manuscripts dating back to pre-Mamluk times", had been ransacked and destroyed.
"Armed terrorist groups have looted and completely destroyed the Islamic library, which is one of the most valuable in the region with an estimated value of hundreds of thousands of Syrian pounds," Abdel Qader al-Shihabi told AFP.
The site has been a place of worship since the 8th century, but the original building was razed by the Mongols in the 13th century, from when the current structure dates.
Elsewhere in Aleppo's UNESCO-listed Old City, fighting raged around the Justice Palace.
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Observatory director Rami Abdel Rahman said that if the rebels gain control of the palace, they would be able to cut off army reinforcements to Aleppo's regime-held citadel.
While rebels have taken over large swathes of territory and a number of key military garrisons in Aleppo province, fighting in the city has been at stalemate for months.
In Homs, "terrorists detonated a car bomb laden with large amounts of explosives in the Akrama Jadideh neighbourhood, killing one civilian and wounding 24 others and causing serious material damage," SANA reported.
The Syrian Observatory said the blast took place near a public swimming pool in government-controlled Akrama.
To the north of Aleppo, air strikes targeted rebel positions around Menegh military airbase, which has been under protracted siege as the opposition battles for control of northern airports.
Warplanes also carried out several raids in Raqa province.
And fierce clashes erupted in Damascus on the outskirts of rebel-held Jobar district in the east and near the Palestinian refugee camp of Yarmuk in the south, said the Observatory.
The watchdog, which gathers its information from a network of activists and medics, said 157 people were killed nationwide on Wednesday.