The ancient cities of Damascus, Basra and Allepo, the Site of Palmyra, the Crac des Chevaliers and Qal'at Salah El-Din, and Ancient Villages of northern Syria were inscribed on the List of World Heritage in Danger by the World Heritage Committee, the U.N. Educational, Scientific and Cultural Organization officials said in a release.
"The danger listing is intended to mobilize all possible support for the safeguarding of these properties, which are recognized by the international community as being of outstanding universal value for humanity as a whole," the organization said.
UNESCO Director-General Irina Bokova has called on both sides of the Syrian conflict to take all precautions to prevent destruction of the country's cultural heritage in the violence that began in March 2011.
In April, there were reports that the minaret of the Great Mosque in Aleppo was reduced to rubble, the United Nations said.
In October, Aleppo's souk -- considered to be the world's most extensive covered market and a tourist destination -- was heavily damaged by fire during a skirmish between the Syrian army and opposition forces seeking to oust President Bashar Assad.
The United Nations said more than 93,000 people have been killed since the civil war began.