Syrian rebel group Jaish al-Islam denied on Tuesday a Russian defence ministry report that its jets had destroyed a stash of oil products belonging to them in areas they control in the eastern suburbs of the Syrian capital.

The group, which is the most powerful rebel faction in the rural eastern suburban area of Damascus, has been a target of heavy Russian bombing since Moscow begin a major military campaign four months ago.

Russian jets are also believed to have killed Jaish al-Islam leader Zahran Alloush in a December raid that targeted the group's headquarters, dealing a major blow to rebel control of the area.

Jaish al-Islam denied the Russian report in an emailed statement received overnight.

The group is one of the main rebel factions represented in the Saudi-backed High Negotiation Committee. It is ideologically at odds with Islamic State and al Qaeda, but is deemed by President Bashar al-Assad and his ally Russia to be a terrorist group.