Human Rights Watch (HRW) has sounded the alarm over what it says is the "extensive" use of cluster bombs in Syria since Russian and Syrian authorities launched their joint military offensive against rebel groups almost three months ago.
In a detailed report, the New York-based watchdog said it had documented 20 cluster-munition attacks in populated areas across the war-torn country since Russian launched its bombardment campaign in Syria on September 30.
Ole Solvang, deputy emergencies director at Human Rights Watch, said those attacks killed 35 civilians, including 17 children, and injured dozens of others.
"The problem with these cluster munitions is that they are inherently indiscriminate," he told RFE/RL. "They fall over a wide area, so civilians in that area can be injured or killed. But many of them also fail to explode and cause a threat to civilians long after the fighting has ended."
"Civilians," he said, "are paying the price of the Syrian-Russian offensive's use of cluster munitions with their lives and limbs."
The report said the actual number of cluster munition attacks to hit Syria in recent weeks was likely much higher, "suggest[ing] that either Russian aircraft dropped them or Russian authorities recently provided the Syrian government with more cluster munitions, or both."
Neither Russia nor Syria is a signatory of the international treaty banning the use of cluster munitions.
But Human Rights Watch said the documented attacks still constitute a violation of international law.
"Using these types of weapons in populated areas is still illegal, even if you are not party to that treaty, because it violates the laws of war," Solvang said.
Human Rights Watch noted older allegations that Syrian President Bashar al-Assad's forces had used such weapons before the Russian military involvement began, saying that "Syrian government forces have used cluster munitions in multiple locations across 10 governorates of the country since mid-2012."
The rights group was not able to determine whether Russian or Syrian government forces were responsible for individual attacks, as they use many of the same weapons and often conduct their operations jointly.
But the report said the evidence undeniably points to their involvement.
It said that "armed opposition groups do not operate aircraft, which means that Russian or Syrian government forces were responsible for the air-dropped cluster munitions."
Human Rights Watch said the four types of ground-fired cluster munitions recently used in Syria were launched from large vehicles that have never been seen in the possession of armed opposition groups.
The group said all the cluster-munition attacks it documented fell on opposition-controlled territories in Syria.
According to the report, the munitions it was able to confirm were all manufactured in the former Soviet Union or Russia.
While a number of attacks appear to have targeted areas with armed groups, the report said strikes have also hit camps for internally displaced people and other populated areas.
According to Human Rights Watch, a cluster bomb fell over a camp in Younseyeh, a village in Idlib province near the Turkish border, on November 9 -- the same day Syrian authorities issued a statement promising not to use indiscriminate weapons.
The group said hospital staff had reported seven civilians dead and dozens wounded.
Another attack reportedly hit two operational schools in Douma, a suburb of Damascus, killing at least eight children.
Human Rights Watch urged Syria and Russia to join the 118 countries that have banned cluster munitions as a threat to civilians.
On December 7, Russia voted against the first-ever resolution by the United Nations General Assembly backing the global ban on cluster bombs.
The resolution was adopted by 139 counties, with 40 abstentions.
The only other country to vote against the resolution was Zimbabwe.
