According to new reports, ISIS has taken near complete control of the ancient Syrian city of Palmyra.
Palmyra is home to some of the world’s most magnificent ruins.
There are fears that the Islamic State militants will destroy the ruins, which UNESCO has designated a World Heritage site.
Syria has admitted it has pulled government troops out of Palmyra following the ISIS advance.
ISIS militants have demolished several ancient sites that pre-date Islam in Iraq, including Hatra and Nimrud.
Syrian state media said pro-government forces had been pulled out of Tadmur, the modern settlement on Palmyra, after “assuring the evacuation” of most of its inhabitants.
Hundreds of Palmyra’s statues have been moved to safety but large monuments from the ancient parts of the city could not be moved.
Rising out of the desert, Palmyra contains the monumental ruins of a great city that was one of the most important cultural centers of the ancient world, according to UNESCO.
The site, most of which dates back to the 1st and 2nd Century when the region was under Roman rule, is dominated by a grand, colonnaded street.
UNESCO’s Director-General Irina Bokova said she was “deeply concerned” by the situation.
“The fighting is putting at risk one of the most significant sites in the Middle East, and its civilian population,” Irina Bokova said in a statement.
Palmyra is situated in a strategically important area on the road between the capital, Damascus, and the contested eastern city of Deir al-Zour, and is close to gas fields.
A United States-led coalition has carried out air strikes on the jihadist group’s positions since September 2014. However, it says it does not co-ordinate its actions with the Syrian government.
Meanwhile, the US said it was sending 1,000 anti-tank missiles to the Iraqi government following the fall of Ramadi to ISIS.