The two purported chemical weapon assaults resemble one claimed Saturday by Kurdish officials who say an independent laboratory concluded the militants used chlorine gas against its peshmerga forces in a Jan. 23 truck suicide attack.
However, their claims were not immediately verified by international authorities.
Iraqi officials and Kurds fighting in Syria have made similar allegations about the militants using the low-grade chemical weapons against them. The Islamic State group, which controls a third of Syria and Iraq in its self-declared caliphate, has not commented on the claims.
Kurdish officials have offered footage of the aftermath of the Dec 26 attack, which shows fighters coughing and pouring water over their heads after another suicide truck bombing that authorities say wounded some 60 men.
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"I put a wet scarf on my face because when I saw the gas, I felt it," said Capt. Mohammad Sewdin, who leads the Kurdish special forces unit targeted in the December attack. "I was afraid it might be something like (chemical weapons). So I told my men to do the same."
On Saturday, the Kurdistan Region Security Council offered video and lab results it said proved the Islamic State group used chlorine in the Jan. 23 suicide truck bomb.
There has been no independent confirmation of any of the Kurds' claims. Peter Sawczak, a spokesman for the Organisation for the Prohibition of Chemical Weapons, which has monitored Syria dismantling its chemical weapons stockpile, said today that no member state had requested an investigation into the Kurdish claims.