Human Right Watch on Thursday said Syrian regime forces appear to be using Soviet-made cluster bombs against rebel hideouts in a mountainous region of Hama province.

Two videos posted online on Tuesday appear to show unexploded submunitions and a bomb canister in Jabal Shahshabu, northwest of the city of Hama, said the New York-based group.

It quoted a local militant as saying the region has come under constant bombardment from the air and ground over the past two weeks, targeting rebels and their cave hideouts.

"These videos show identifiable cluster bombs and submunitions," said Steve Goose, arms division director at HRW.

"If confirmed, this would be the first documented use of these highly dangerous weapons by the Syrian armed forces during the conflict," said Goose.

HRW said its own arms experts and from the Geneva International Centre for Humanitarian Demining said that one video showed the remnants of a RBK-250 series cluster bomb canister.

The other shows unexploded 15 AO-1Sch submunitions, small fragmentation bomblets that are delivered by RBK bombs, it said.

"The RBK-250 series cluster bomb can only be delivered from a warplane because of its size and the speed necessary for its submunitions to be deployed correctly," HRW said.

More than 100 countries, not including Syria, have signed a Convention on Cluster Munitions that entered into force on August 1, 2010. It requires signatories to stop the use, production and transfer of the weapons.

Many cluster bombs fail to explode immediately, lie hidden for years and kill and maim civilians.