The Islamic terrorist group ISIS, attempting to solidify their takeover of the ancient city of Palmyra, have forced the residents of the town to fill an ancient amphitheater to watch the execution of 20 men.

The Syrian Observatory for Human Rights said the men were accused of serving as members of the army for President Bashir al-Assad.  The method of execution was not reported by the group.

The United Nations World Heritage site was overrun by the terrorists last week.  The U.N. also reported that residents told them the Syrian government forced them to remain until all troops withdrew from the city, placing them at the mercy of the terrorists.

The terrorists have also killed 67 civilians, including 14 children and 12 women, in the city of al-Sikhni.  The terrorists said they were harboring regime forces to hide them from ISIS.

The UN has also reported that the terrorists burned a young woman alive because she would not be used as a sex slave by the group.

“They are institutionalizing sexual violence,” Zainab Bangura, the U.N.’s special representative on sexual violence in conflict, said of the Islamic State. “The brutalization of women and girls is central to their ideology.”