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.