ISIS militants blew up a Syrian temple Sunday in the ancient city of Palmyra, one of the most important sites in the city's history dating all the way back to the Roman era, according to NBC News.

Witnesses say that ISIS planted explosives from the building's inner area causing major damage.

The militant group destroyed the temple because it considers statues and grave markers to be idolatrous. ISIS has been destroying antiquities and heritage sites in territories under its control in Syria and Iraq, according to the Guardian.

Syrian officials said that they were able to move hundreds of statues to a safe location before ISIS took over the city, but much of the city's archaeological history and treasures were left behind, as well as thousands of residents, according to the New York Times.

The now-destroyed ancient temple of Baal Shamin was built in 17AD in honor of the Phoenician god Baalshamin and was later expanded under the reign of Roman emperor Hadrian in 130AD. 

Last week, ISIS killed 83-year-old Khalid al-Asaad, who served as the city's chief of antiquities for more than 50 years, as previously reported by HNGN. The group kept Asaad as their captive for more than a month before they eventually beheaded him and strung up his headless body as a warning for all to see.