One of Syria's oldest and largest mosques, the Umayyad Mosque in the old city of Aleppo, was set on fire over the weekend as government troops and rebel fighters waged fierce battles for control.

Dating back to the 12th Century, the mosque has been caught in the crossfire of Syria's civil war because of its strategic location in the heart of downtown Aleppo.

Last week, Unesco appealed for the protection of the world heritage-listed site, which it described as "one of the most beautiful mosques in the Muslim world".

It was originally founded in the early Islamic period but little had remained of the original structure after it was destroyed during the Mongol invasion of 1260.

Syrian TV reported on Monday that President Bashar al-Assad had ordered immediate repairs to the damaged mosque, also known as Jami al-Kabir.

Amateur videos posted online revealed the damage. Eyewitnesses said they saw black smoke rising from it at the weekend.