Director-General of the UN Educational, Scientific and Cultural Organization Irina Bokova on Thursday condemned the destruction of parts of the ancient Syrian city of Bosra, a World Heritage site, in fighting earlier this week, UN spokesman Stephane Dujarric told reporters.

"Ms Bokova said that the destruction represents a further escalation in the horror of war and must be stopped at once to preserve the irreplaceable heritage of Bosra," Dujarric said at a daily news conference.

Bosra, once the capital of the Roman province of Arabia and an important stopover on the ancient caravan route to Mecca, Saudi Arabia, was inscribed on UNESCO's World Heritage list in 1980.