Islamic State militants in northern Syria have blown up another monument in the ancient city of Palmyra, officials and local sources say.
The Arch of Triumph was "pulverized" by the militants who control the city, a Palmyra activist said.
It is thought to have been built about 2,000 years ago, BBC reports.
IS fighters have 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. IS has destroyed it," Mohammad Hassan al-Homsi, an activist from Palmyra, said on Monday.
The London-based Syrian Observatory for Human Rights, a group monitoring the conflict, said sources on the ground had confirmed the destruction.
Syrian antiquities chief Maamoun Abdul Karim also confirmed the news, and told Reuters that if IS 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".
IS believes shrines or statues represent idolatry, and should be destroyed.
In August, the group destroyed the ancient Temple of Baalshamin–one of the city's best-known buildings built nearly 2,000 years ago.
- Militants Flee Syrian Army
Scores of IS militants have reportedly fled Syria in fear of an upcoming large-scale Syrian Army offensive.
More than 3,000 militants from the IS, Jabhat Al-Nusra and Jaish al-Yarmouk groups have left Syria for Jordan, fearing the forthcoming Syrian Army offensive, Russia's news agency Ria Novosti quoted a military source as saying.
"At least 3,000 militants from the Islamic State, the Al-Nusra and the Jaish Al-Yarmouk fled to Jordan. They are afraid of the army's advance on all fronts and the Russian aircraft airstrikes," the source said.
According to the source, the Syrian Army on Sunday attacked militants from the IS and the Jabhat Al-Nusra" in the suburbs of the capital Damascus and the provinces of Deir Ezzor and Homs, as well as near the city of Palmyra.
In Deir Ezzor, about 160 militants were reportedly killed during the fighting, while the army's assault on Holms and Palmyra left at least 17 militants dead.
- Target All Terrorists
French Foreign Minister Laurent Fabius said Monday that airstrikes in Syria must target IS militants but also other groups "considered as terrorists."
Fabius said a statement by President Francois Hollande on Friday that Russian airstrikes must target "IS and only IS", did not exclude other groups like the Al-Nusra Front.
"Of course, it is a concise formulation, it is IS and groups considered as terrorists," Fabius told Europe 1 radio in an interview, referring to Hollande's statement.
Moscow, which has launched more than 70 airstrikes in Syria since last Wednesday, has come under fire for targeting Western-backed moderate opposition and IS fighters alike in their bid to bolster Syrian President Bashar Al-Assad.
US President Barack Obama has called Russia's dramatic intervention a "recipe for disaster", while British Prime Minister David Cameron urged Russian President Vladimir Putin on Sunday to "change direction" in Syria and recognize that Assad must be replaced.
France, which has been targeting IS in Iraq for the past year, began striking the group in Syria eight days ago.
