US confirms IS used chemical rocket in attack on troops in Iraq

An offensive to retake Mosul from IS is expected in the coming weeks

A rocket launched by Islamic State militants at American troops based in Iraq did contain a mustard agent, the US military has confirmed.

No-one was hurt in Tuesday's attack on the Qayyarah air base near the IS stronghold of Mosul.

Marine Gen Joseph Dunford, chairman of US joint chiefs of staff, said the group's capability to deliver chemical weapons was rudimentary.

But the attack, he added, was a "concerning development".

IS has long been suspected of making and using crude chemical weapons in Iraq and Syria, where it also controls territory.

• 'IS making and using chemical weapons'

• Islamic State and chemical weapons use

• Inside Iraqi town hit by 'IS chemical attack'

Gen Dunford told the US Senate armed services committee on Thursday that the rocket had contained a "sulphur-mustard blister agent".

Mustard agent in sufficient quantities can maim or kill by damaging skin, eyes and airways.

Mosul, Iraq's second largest city, has been under IS control for the past two years and the battle to retake it is expected to begin in the coming weeks.

US troops are providing assistance to local forces as they prepare for the offensive.