UNITED NATIONS, June 23 (Reuters) - The Syrian opposition High Negotiations Committee (HNC) called on United Nations Secretary-General Ban Ki-moon on Thursday to launch an investigation into its accusations that Russia has repeatedly used air-delivered incendiary weapons in Syria.
Russia deployed warplanes to Syria last year to support President Bashar al-Assad against rebels seeking to end his rule. A crackdown by Assad on pro-democracy protesters five years ago sparked a civil war and Islamic State militants have used the chaos to seize territory in Syria and Iraq.
"Russian air forces have repeatedly deployed incendiary weapons and cluster munitions to kill, main and terrorize Syrian civilians, including in at least 10 documented incidents," Riad Hijab, coordinator of the opposition HNC, wrote to Ban.
"They have violated the Convention on Certain Conventional Weapons and breached international humanitarian law," he wrote.
Hijab alleged that "thermite, which ignites while falling, has been likened to 'mini nuclear bombs' and was deployed repeatedly by Russian forces in residential areas." He also accused Russian forces of using cluster munitions.
Incendiary weapons use substances that are designed to set fire to objects or burn people, and cluster munitions are containers that explode in the air to distribute smaller bombs over a large area. Both are banned under the convention.
The Russian mission to the United Nations was not immediately available to comment on the accusations. Ban's office was also not immediately available to comment on the request for an investigation.
State Department spokesman John Kirby told reporters in Washington that the United States was not in a position to confirm the allegations by the Syrian opposition, but that the claims were taken very seriously.
"Regardless of what weapons they're using, (the Russians) shouldn't be striking groups that are committed to the counter-ISIL fight or civilians," he added. "Russia and the Assad regime need to be more careful about distinguishing between terrorists, civilians and parties to the cessation of hostilities."
The United States has sharply criticized Moscow over strikes last week against U.S.-backed forces in Syria, saying Russia failed to heed U.S. warnings to stop its attack, which killed and injured Syrian fighters battling Islamic State.
U.S.-backed forces in Syria have reported that Russia fired at their garrison with cluster munitions in that attack, a senior British general in the U.S.-led coalition said on Thursday.
"Definitely, the people we advise on the ground reported cluster munitions," British Army Major General Doug Chalmers told a Pentagon news conference.
(Reporting by Michelle Nichols, Arshad Mohammed and Phil Stewart; Editing by Cynthia Osterman)
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