The Daesh jihadist group executed at least 20 men in the ruins of Syria's Palmyra on Wednesday, accusing them of fighting for the government, a monitoring group said.

"Daesh 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," Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, told AFP.