ISIS militants have blown up the Arch of Triumph in the ancient city of Palmyra, Syrian officials and local sources say.

The Arch of Triumph was “pulverized” by the ISIS fighters who control the city, a Palmyra activist told AFP.

The monument is thought to have been built about 2,000 years ago.

ISIS has already destroyed two ancient temples at the site, described by UNESCO as one of the most important cultural centers of the ancient world.

“The Arch of Triumph was pulverized. ISIS has destroyed it,” Mohammad Hassan al-Homsi, an activist from Palmyra told AFP on October 5.

The Syrian Observatory for Human Rights, a group monitoring the conflict, said sources on the ground had confirmed the destruction.

Syrian antiquities chief Maamoun Abdulkarim also confirmed the news, and told Reuters news agency that if ISIS remains in control of Palmyra, “the city is doomed”.

UNESCO’s director general Irina Bokova has said the destruction constitutes a “war crime” and called on the international community to stand united against IS efforts to “deprive the Syrian people of its knowledge, its identity and history”.

ISIS believes shrines or statues represent idolatry, and should be destroyed.

In August, ISIS destroyed the ancient Temple of Baalshamin – one of the city’s best-known buildings built nearly 2,000 years ago.

The group has also published photos of militants destroying what it said were artifacts looted at Palmyra.

ISIS militants captured the historic site from Syrian government troops in May, amid a series of setbacks for forces loyal to President Bashar al-Assad.

Syria’s conflict, which began in 2011, has left more than 250,000 dead and about half the country’s population displaced.