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Russia says that chemical gas that killed and injured dozens of civilians in a rebel-held town in northern Syria came from rebel weapons on the ground, the BBC reports.

Its defence ministry acknowledged that Syrian planes had attacked the town of Khan Sheikhoun in Idlib province.

But it said the aircraft had struck a depot producing mines filled with a poisonous substance, for use in Iraq.

The US and others said Syrian planes had dropped chemical weapons, which Damascus denied.

UK-based monitoring group the Syrian Observatory for Human Rights put the death toll in Khan Sheikhoun at 72, including 20 children.