A picture taken on March 14, 2014, shows columns in the courtyard of the Temple of Baal at the ancient city of Palmyra, damaged by artillary shelling in the ancient oasis city of Palmyra, 215 kilometres northeast of Damascus. JOSEPH EID/AFP/Getty Images

The extent of damage to the Temple of Baal in Palmyra was unclear Monday after the Islamic State group attempted to blow up the historic structure, a Syrian official said. An ISIS operative who spoke with the Associated Press over Skype said the group had detonated explosive devices but would not reveal how much of the site had been damaged.

ISIS has set out to destroy cultural heritage sites in Iraq and Syria since the group took control of territory in both nations in 2014. In March, the United Nations called the destruction of shared cultural heritage sites a “war crime.”

The Temple of Baal is a 2,000-year-old Unesco world heritage site in the ancient city of Palmyra. ISIS has held Palmyra for three months and had already destroyed the Temple of Baalshamin.

A general view shows the temple of Baalshamin in the historic city of Palmyra, Syria, Oct. 26, 2009. ISIS has destroyed the temple. REUTERS/Stringer

An expert on Islamic art told Intertional Business Times last week the destruction of sites in Palmyra shows how ISIS wants to destroy a “cosmopolitan culture that celebrated difference.” Many of the ancient sites represent pre-Islamic groups, another reason experts say the group is motivated to destroy them. The group has also looted sites and attempted to sell artifacts to fund its terrorist activities.

In Iraq, ISIS released videos of destruction of the ancient sites of Hatra and Nimrud in March. At the time of the destruction U.S. Secretary of State John Kerry issued a statement saying, “These depraved acts are an assault on the heritage of the Iraqi and Syrian people by an organization with a bankrupt and toxic ideology.”

This 2003 picture shows the court of the royal palace in the ancient city of Hatra in Iraq. PHILIPPE DESMAZES/AFP/Getty Images

Only days after the destruction of Hatra and Nimrud in March, ISIS reportedly destroyed Khorsabad, an ancient Assyrian capital, located in Iraq.

The Temple of the Sibitti in Khorsabad, Iraq, (pictured) was the site of Dur Sharrukin, the capital of the Assyrian Empire in the late 8th century B.C. during the reign of Sargon II. ISIS militants reportedly wrecked the archaeological site. Vivienne Sharp/Heritage Images/Getty Images

In March, ISIS also destroyed artifacts in the Mosul Museum in Iraq, but it was later reported those artifacts were not the original pieces. The original works are under safekeeping in a museum in Baghdad. In Mosul, ISIS also targeted the Tomb of Jonah destroying the structure.

An artifact coming from the area of Mosul and dating back to the second century B.C is displayed during the official reopening of Iraq's national museum, Feb. 28, 2015, in Baghdad. The originals of many artifacts destroyed by ISIS in Mosul are under safekeeping in Baghdad. SABAH ARAR/AFP/Getty Images

Experts fear ISIS could also have destroyed sites in Assur, Iraq, the first Assyrian capital. After years of war, any sites that remain in Aleppo, Syria, could also be future targets.