WATCH: Syria's Assad accused of using cluster bombs against civilians
Dropped by planes or helicopters, the bombs explode in the air and scatter to dozens of bomblets over an area the size of a sports field; International law bans use of such weapons.
Syrian government forces have dropped Russian-made cluster bombs over civilian areas in the past week as they battle to push back rebel gains, Human Rights Watch said on Sunday.
The bombs were dropped from planes and helicopters, with many of the strikes taking place near the main north-south highway running through the northwestern town of Maarat al-Numan, HRW said in a report.
Rebels seized Maarat al-Numan from President Bashar Assad's troops last week, cutting the route from the capital Damascus to Aleppo, Syria's biggest city. Government forces have been trying to retake the area since then.
HRW previously reported Syrian use of cluster bombs, which have been banned by most countries, in July and August but the renewed strikes indicate the government's determination to regain strategic control in the northwest.
Towns targeted included Maarat, Tamanea, Taftanaz and al-Tah. Cluster bombs were also used in other areas in Homs, Aleppo and Lattakia provinces as well as near Damascus, the rights group said.
"Syria's disregard for its civilian population is all too evident in its air campaign, which now apparently includes dropping these deadly cluster bombs into populated areas," said Steve Goose, arms director at HRW.
Initial information about the use of the explosives came from videos posted online by opposition activists although HRW investigators said it had confirmed the incidents in interviews with resident in two towns.
It had no information on casualties. The cluster bombs were Russian-made but it was not known how or when Syria acquired them, New York-based HRW said.
Residents from Taftanaz and Tamanea - both near Maarat al-Numan - told HRW interviewers that helicopters dropped cluster munitions on or near their towns last Tuesday. One that hit Tamanea released smaller bomblets in an area between two schools, a resident was quoted as saying in the HRW report.
"The bomblets that exploded were the ones that hit the ground on the tip, we collected the ones that didn't explode, their tip didn't touch the ground," the resident said.
People were taking away unexploded bomblets as souvenirs, a highly dangerous action as they can still explode at the slightest touch or movement. Video showed some civilians carrying the bomblets around and throwing them on the ground.
"The cluster munition strikes and unexploded ordnance they leave behind pose a huge danger to civilian populations, who often seem unaware how easily these submunitions could still explode," Goose said.
Cluster bombs explode in the air, scattering dozens of smaller bomblets over an area the size of a sports field. Most nations have banned their use under a convention which became international law in 2010, but Syria has not signed it.
Syrian government officials were not immediately available to comment on the HRW report.