News of the killings comes as US President Barack Obama is reportedly weighing air strikes on IS positions in Syria and coming closer to greenlighting a mission to aid Shiite Turkmen trapped in an Iraqi town by the jihadists.
Syrian regime air strikes killed six IS leaders today, the Syrian Observatory for Human Rights said, but Washington has so far baulked at cooperating with Damascus against the jihadists.
The latest killings took place in the Syrian province of Raqa, the Syrian Observatory for Human Rights said, adding that the victims were soldiers fleeing towards government-held territory to the west after the jihadists overran their base at Tabqa.
The jihadists boasted on Twitter that they had killed 200 defeated troops and posted video of what they said was the garrison in headlong flight.
Also Read
"IS executed more than 160 Syrian soldiers in three different places in Raqa province yesterday and at dawn today," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.
Abdel Rahman said the defeated garrison comprised 1,400 soldiers, 200 of whom were killed and 700 of whom managed to escape.
Of the other 500, dozens were captured on Wednesday night as they attempted to cross the desert to government-held territory in the Orontes Valley to the west.