Beirut: At least 37 people, including 10 children, were killed in government barrel bomb attacks in northern Syria today, a monitoring group said. The Syrian Observatory for Human Rights said the deaths came in three incidents, in Aleppo province in the north and Idlib province in the northwest.

In Tal Rifaat in Aleppo, 18 people were killed, including eight children, when government helicopters dropped at least four of the devices, the Britain-based monitor said. In the rebel-held eastern neighbourhood of Jubb al-Qubbeh in Aleppo city, 11 civilians died, among them two children, when a barrel bomb exploded.

And in Idlib province, eight members of one family were killed in a barrel bomb attack in the town of Kafr Sijna. The Observatory, which relies on a network of sources on the ground, said the tolls in the incidents were expected to rise because of the number of people seriously wounded.

Regime barrel bombs -- crude weapons made of containers packed with explosives -- have often hit schools, hospitals and markets in Syria. Rights groups criticise them as indiscriminate, saying they kill a disproportionate number of civilians.

Syrian President Bashar al-Assad has denied that his forces use the weapons, but evidence collected by activists and rights groups includes footage of the barrels being pushed from helicopters. Human Rights Watch has also said there is "strong evidence" the regime has dropped barrel bombs containing toxic chemicals on northern Syria.

The New York-based group said today that it had led an investigation into three attacks in Idlib province, which killed two people and affected 127 others, and that deadly chlorine was probably used in some, if not all of them. "The Syrian government has used barrel bombs with toxic chemicals for more than a year while the (UN) Security Council has failed to act," said Philippe Bolopion, HRW's UN and crisis advocacy director.

Meanwhile, the extremist Islamic State group pressed its assault on the northeast Syrian city of Hasakeh, detonating at least five car bombs as it advanced towards the city. "IS blew up five booby-trapped vehicles in various locations south of Hasakeh," Observatory head Rami Abdel Rahman said, adding that there were also fierce clashes.