Government soldiers have been seriously injured after ISIS reportedly used mustard gas during a fierce battle for a key airport in Syria, it has been reported.
Harrowing footage showing Syrian fighters struggling to breathe and being carried away on stretchers has been shared online, with Syrian state news saying the attack happened on Monday.
Fighting was taking place at a military airport in Deir ez-Zor when ISIS fired rockets containing the deadly nerve agent, state-owned news agency Sana reported.
The airport is one of the few remaining assets still held by the Syrian government in the north-eastern province , which is otherwise controlled by ISIS.
It is unclear how many troops were injured or killed in the attack.
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Last month ISIS used chemical weapons on the Iraqui town of Taza, killing three children and injuring an estimated 600 people.
The terror group is believed to have set up a special unit for researching chemical weapons, headed up by Sleiman Daoud al-Afari, a chemical engineer who previously worked for Saddam Hussein .
He was captured last month by US soldiers , supposedly striking a blow to the terrorist group's biological weapons programme.