The Syrian army claimed that an air strike late yesterday by the US-led coalition hit poison gas supplies belonging to ISIS , and released a toxic substance that killed "hundreds including many civilians".

The incident in the eastern Deir al-Zor province proved that ISIS and al-Qaeda-linked militants "possess chemical weapons", a statement by the army publicized on Syrian state TV claimed, adding that these weapons had been obtained from "countries in the region which are well known."

The report could not immediately be independently verified and the US has denied that it attacked any ISIS chemical weapons site.

Last week the US launched cruise missiles at a Syrian airbase , in response to a deadly poison gas attack in the west of the country that Washington blamed on President Bashar al-Assad's government.

Syria and its ally Russia deny that Damascus carried out any such chemical attack. Assad even claims that the US 'fabricated' the chemical attack, while Moscow has said the poison gas in that incident last week in Idlib province belonged to rebels.

The US strike on the Syrian air base last Thursday was the first time Washington has deliberately and directly targeted the Syrian government.