ISIS has shot dead at least 20 people in the Roman amphitheatre of the Syrian city of Palmyra, a monitoring group said.
Syrian Observatory for Human Rights, which tracks the conflict from Britain through contacts on the ground reported on Wednesday that ISIS militants killed around 20 men, accused by the group of being government supporters.
"ISIS executed 20 men by firing on them in front of a crowd gathered in Palmyra's Roman theatre, after accusing them of fighting for the Syrian regime," said the Observatory’s chief, Rami Abdulrahman.
ISIS captured Palmyra, a UNESCO world heritage site dating back to Roman Empire, on May 21.
It marked the first time the group seized a government-controlled city.
ISIS militants have so far killed 217 people in the city, according to the Observatory.
ISIS now controls more than half of Syrian territory after seizing Palmyra. The country’s main population centres, such as Damascus, Aleppo and Homs are under the government’s control.