A U.N. agency says satellite imagery shows that at least 290 cultural heritage sites in Syria have been damaged by the country's civil war.

The United Nations Institute for Training and Research says in its report released Tuesday that UNESCO World Heritage sites in Aleppo, Damascus, the ancient city of Palmyra and the Crusader castle known as Crac des Chevaliers have all sustained major damage.

UNITAR says it analyzed 18 different cultural areas using commercially available satellite imagery. It found that 24 sites were destroyed, 104 severely damaged, 85 moderately damaged and 77 possibly damaged.

UNITAR says "national and international efforts for the protection of these areas need to be scaled up in order to save as much as possible of this important heritage to human-kind."