BEIRUT: Six children were among at least 57 people killed in southern Syria as the army launched an all-out assault on two towns in Daraa province, a watchdog said on Thursday.

“At least six children, seven women, 16 rebel fighters, 16 other unidentified men and 12 army troops were killed on Wednesday, in fighting, shelling and summary executions waged after the army launched an assault on Al-Sanamein and Ghabagheb,” the Syrian Observatory for Human Rights said.

Observatory director Rami Abdel Rahman told AFP the army's assault came a day after a dozen troops defected from a nearby military post to join the rebels.

“The defectors took refuge in the area of Al-Sanamein and Ghabagheb, which up until then had remained somewhat more calm than other areas of Daraa,” said Abdel Rahman.

“The army launched its assault, and shelled several houses,” he added.

Nationwide, at least 179 people were killed in violence on Wednesday — 50 civilians, 86 rebels and 43 soldiers, the Observatory said.

On Thursday, at least four military personnel were killed when rebels shot down a helicopter delivering supplies to besieged troops in Idlib province in the northwest, the Observatory said.

Rebels have laid siege to the sprawling Wadi Deif camp for several months and its garrison can only be resupplied by air.

Amateur video footage distributed by the Observatory showed onlookers gathered around at least three bloodied corpses in an open field.