The Islamic State group, also known as ISIS, targeted the ancient Syrian city of Palmyra by destroying parts of the Roman amphitheater and a tetrapylon — a four-sided monument — state-run Syrian Arab News Agency (SANA) reported Friday.

The militant group blew up the facade of the Unesco World Heritage site — build in the second century — and the tetrapylon, SANA reported, without giving details about how the monuments were destroyed. Satellite images of the destroyed monuments were released by the United Nations Institute for Training and Research.

Palmyra Tetrapylon Tetrapylon, the four-sided Roman monument, is seen in ancient Syrian city of Palmyra, April 30, 2005.

ISIS regained control over Palmyra in December 2016 after Russian-backed Syrian armed forces pulled out of the historic city. During its initial occupation in May 2015, the extremist group destroyed prominent monuments in the centuries-old city located in the western governorate of Homs, triggering international uproar.

In 2015, ISIS used the ancient amphitheater in Palmyra, also known as the “Pearl of the Desert,” as a place to carry out public executions, including the beheading of Khaled Asaad, who was the city’s 82-year-old former antiquities chief.

Losses in Palmyra include the Elahbel Tomb, Baal Shamin Temple, Temple of Bel, the Valley of the Tombs, as well as several statues and artifacts, most of which date from the first or second century A.D. The group also blew up the Arch of Triumph, a popular monument, and Palmyra’s funeral towers, which were sandstone structures built to house the remains of the 2,000-year-old city’s richest families.

Repair work for damaged structures began after Syrian government forces retook Palmyra in March 2016.