Syria’s regime are expanding its use of cluster munitions in its conflict with rebel forces, causing “mounting civilian causalities,” Human Rights Watch warned on Saturday.

“Syria is expanding its relentless use of cluster munitions, a banned weapon, and civilians are paying the price with their lives and limbs,” Steve Goose, director of HRW’s arms division, said in a statement.

The watchdog said it had identified at least 119 places across Syria where at least 156 cluster bombs have been used in the past six months, including two attacks in the last two weeks that killed 11 civilians and injured 27 others.

“The initial toll is only the beginning because cluster munitions often leave unexploded bomblets that kill and maim long afterward,” Goose added. The New York-based rights group said its data was collected from field investigations and analysis of videos posted online by activists.

It said it had documented government use of cluster munitions, but had no evidence rebels were using them.

Syria is not party to the Convention on Cluster Munitions, which restricts use of the weapons, but HRW urged signatory nations to speak out against the regime’s use of the munitions.

“All nations that have joined the treaty banning cluster bombs have a legal obligation to speak out and condemn Syria’s ever-expanding use of these indiscriminate weapons, yet too few are doing so,” Goose said.

The statement came as Syria’s civil war, which began with peaceful anti-government demonstrations in March 2011, entered its third year.  The conflict has killed at least 70,000 people, and forced more than one million Syrians to seek refuge abroad.