The Islamic State may have used chemical agents in an attack against civilians and rival insurgents in northern Syria late last week, according to local rebels and an international aid group.
The assault on Friday in the city of Marea involved more than 50 shells and was centered on civilian areas, the Syrian American Medical Society, a humanitarian group, reported.
After the attack, the group’s field hospital received more than 50 patients, 23 of whom, including some children, showed symptoms of chemical exposure, including coughing, vomiting, wheezing and severe itching. Some also had blisters associated with mustard gas, the society said in a statement.
The report was corroborated by local rebel forces, who claimed that shells had been fired from Isnibil, a village east of Marea that is controlled by the Islamic State, also known as ISIS or ISIL.
“At least half of the 50 mortar and artillery shells fired by ISIS contained poisonous mustard gas,” said Hussein Nasir, a spokesman for a Syrian rebel group, the Shami Front.
He said that his group had consulted a general who defected from the Syrian Army and was familiar with chemical weapons. After hearing accounts of the attack and seeing videos and photographs of the shells, the general concluded that some of the shells contained mustard gas, Mr. Nasir said.
This month, the Pentagon said the Islamic State was suspected of using chemical agents in an attack against Kurdish forces in northern Syria. American officials said they were also looking into reports of a mustard gas attack on Kurdish fighters in Makhmur, Iraq.
“The shells landed randomly on different parts of the city resulting in many injuries,” Mr. Nasir said of the attack on Friday. “Some bad odor filled the air, and those who were exposed showed symptoms of suffocation, skin irritation and swelling.”
When the shells hit, opponents of the Syrian government of President Bashar al-Assad were commemorating the second anniversary of a chemical weapons attack on a Damascus suburb carried out by the government.
A nurse at the field hospital run by the Syrian American Medical Society said he had noticed a strange odor on the clothes of the victims.
“We received a family in very bad condition, two parents and a child,” the nurse, Tariq Najjar, said. “They had difficulty breathing, severe headaches, a running nose, skin irritation and red teary eyes.”
He said that five more shells were fired on Saturday.
One person was killed in the attack, but apparently by conventional ordnance, not chemical agents, the rebels said. The medical society said in a statement that there had been no deaths from chemical agents.
Marea links the much larger city of Aleppo to the Turkish border, and it is a crucial strategic prize for the Islamic State; many of its residents have fled the fighting.
The city has long been held by insurgents, who initially took up arms against Mr. Assad’s government but have also clashed with the Islamic State. Marea was one of the first strongholds of the rebel forces that were then made up of army defectors and townspeople.