US: IS may use chemical weapons in Mosul fighting

Islamic State [IS] militants may use crude chemical weapons to repel the Iraqi-led offensive on Mosul, Reuters quoted US officials as sayign on Wednesday.

Officials said US forces in Iraq regularly collect and test shell fragments for possible chemical agents, after it was revealed that the militant group previously used mustard agent in attacks, Reuters reported.

Earlier this month, US forces found sulphur mustard agent on fragments of shells fired by IS on local forces, a US official told Reuters.

"Given [IS's] reprehensible behaviour and flagrant disregard for international standards and norms, this event is not surprising," the official said.

At low doses, Sulfur mustard agents can cause burning on exposed skin but would not be lethal.

US officials believe IS has not yet been successful at developing chemical weapons with deadly effects.

On Tuesday, aid groups warned that IS may resort to the use of chemical weapons in Mosul, adding that they were bracing for a humanitarian crisis.

"There are real fears that the offensive to retake Mosul could produce a humanitarian catastrophe," a UN refugee agency spokesman said.

The Red Cross said it was training healthcare workers around Mosul to deal with potential individuals exposed to chemical agents.

Iraqi troops and police have been joined on the battlefront by an array of sometimes rival forces, including the Kurdish Peshmerga, Sunni tribal fighters and Iran-backed Shia militia.

IS once controlled more than a third of Iraq's territory but its self-proclaimed "state" has been shrinking steadily.

Experts say the militants are likely to increasingly turn to insurgent tactics as they lose ground.