Security and hospital officials say the latest attack took place early Saturday in the small town of Taza, which was also struck by a barrage of rockets carrying chemicals three days earlier.
“What the Daesh terrorist gangs did in the city of Taza will not go unpunished,” Iraqi Prime Minister Haider Abadi said, using an Arab acronym for Islamic State during a meeting with local elders Saturday in Taza. “The perpetrators will pay dearly.”
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Sameer Wais, whose daughter Fatima was killed in the first attack, is a member of a Shiite militia fighting Islamic State in Kirkuk province. He said he was on duty on the front lines when the attack occurred early in the morning. He quickly ran home, where he said he could still smell the chemicals in the rocket.
"We took her to the clinic and they said that she needed to go to a hospital in Kirkuk. And that's what we did, we brought her here to the hospital in Kirkuk," he said.
Wais said his daughter appeared better the next day, so they took her home. "But by midnight she started to get worse. Her face puffed up and her eyes bulged. Then she turned black and pieces of her skin started to come off," he said.
By the next morning, Fatima had died, Wais said.
The hundreds of wounded are suffering from infected burns, suffocation and dehydration, said Helmi Hamdi, a nurse at the Taza hospital. He said eight people were transferred to Baghdad for treatment.
"There is fear and panic among the women and children," said Adel Hussein, a local official in Taza. "They're calling for the central government to save them." Hussein said a German and an American forensics team arrived in the area to test for the presence of chemical agents.
U.S. and Iraqi officials said a raid last month by U.S. special forces in northern Iraq captured the head of the Islamic State unit trying to develop chemical weapons.
The U.S.-led coalition said the chemicals Islamic State has so far used include chlorine and a low-grade sulfur mustard that is not very potent. "It's a legitimate threat. It's not a high threat. We're not, frankly, losing too much sleep over it," U.S. Army Col. Steve Warren told reporters Friday.
Experts also say the extremist group appears incapable of launching a large-scale chemical attack, which requires not only expertise, but also the proper equipment, materials and a supply-chain to produce enough of the chemical agent to pose a significant threat.
The coalition began targeting Islamic State's chemical weapons infrastructure with airstrikes and special operations raids two months ago, Iraqi intelligence officials and a Western security official in Baghdad told the AP.
Airstrikes are targeting laboratories and equipment, and further special forces raids targeting chemical weapons experts are planned, the officials said. They spoke on condition of anonymity because they were not authorized to brief reporters.
The extremist group is believed to have set up a special unit for chemical weapons research made up of Iraqi scientists who worked on weapons programs under Saddam Hussein as well as foreign experts.
The group is believed to have created limited amounts of mustard gas. Tests confirmed mustard gas was used in a town in Syria when Islamic State was launching attacks there in August 2015. There have been other unverified reports of Islamic State using chemical agents on battlefields in Syria and Iraq.
Separately, attacks across Baghdad on Saturday killed 13 and wounded 27. The attacks were mostly carried out with homemade bombs placed along roads in the capital's southern and eastern neighborhoods. There were no immediate claims of responsibility, but Islamic State often claims responsibility for bomb attacks in the Iraq capital targeting civilians. As the group has endured territorial losses in Iraq — most recently the city of Ramadi, which was declared "fully liberated" by Iraqi and U.S. officials last month — they have stepped up insurgent-style attacks in Baghdad and other areas far from the front lines.
Hamish De Bretton Gordon, a former British army officer and chemical weapons expert, says the use of chemical weapons by Islamic State also appears to be linked to losses on the battlefield.
"As they get more and more pushed, we're seeing them use it more and more often," he said. "They are trying to prevent defeat."
Wais, Fatima's father, said he was planning to return to the front line against Islamic State as soon as possible. "Now I will fight Daesh more than before, for Fatima."