The United Nations is concerned by the Syrian opposition's accusations that incendiary weapons have been used in Syria but said on Friday it is unable to verify the reports.
The Syrian opposition High Negotiations Committee called on UN Secretary-General Ban Ki-moon on Thursday to launch an investigation into its accusations that Russia has used air-delivered incendiary weapons and cluster bombs in Syria.
The Russian mission to the United Nations was not immediately available to comment on the accusations.
"We are concerned about the reports of the use of incendiary weapons in Aleppo, Syria," UN spokesman Farhan Haq said. "We are not in a position to verify these reports."
"We expect that all parties and states involved in the conflict will refrain from their use in this way," he said.
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.
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 on Conventional Weapons.
