The UN cultural agency on Thursday placed two ancient cities in conflict-torn Yemen, Sana'a and Shibam, on its list of endangered World Heritage sites.
UNESCO said Sana'a, known for its many Islamic sites and multi-storey rammed earth houses, "sustained serious damage due to armed conflict" between Iran-backed rebels and the beleaguered Saudi-supported government.
The UN Educational, Scientific and Cultural Organization said the Qasimi neighbourhood near the urban garden of Miqshamat al Qasimi had sustained "particularly serious damage".
UNESCO is meeting through July 8 in the northwest city of Bonn where it will consider at least 36 natural and cultural sites vying to get World Heritage status.
The 12th century al-Mahdi Mosque has also been affected and "the majority of the colourful, decorated doors and window panes characteristic of the city's domestic architecture have been shattered or damaged", it said.
Signup to our newsletter and follow us on Facebook and Twitter!
The old city of Sana'a has been inhabited for more than 2,500 years and was a major centre for the propagation of Islam, boasting more than 100 mosques, 14 public baths and more than 6,000 houses built before the 11th century.
UNESCO's World Heritage Committee also decided that the old walled city of Shibam was "under potential threat from the armed conflict".
The fighting "compounds safeguarding and management problems already observed", it said as it added the 16th century city to its List of World Heritage in Danger.
Shibam's tower-like structures rise up from a cliff and have given the city the nickname of the "Manhattan of the desert".
The UN on Wednesday declared its highest level of humanitarian emergency in the impoverished Arabian Peninsula country, where more than 2,600 people have been killed since March.