Washington is seeking more information on reports that Islamic State militants used chlorine gas against Iraqi police officers last month, US Secretary of State John Kerry said Friday.

The top US diplomat told reporters he could not confirm the reports, but said the United States took all such "allegations very seriously."

The Washington Post reported Friday that 11 Iraqi police offices had been rushed to a hospital some 50 miles (80 kilometers) north of Baghdad last month suffering from dizziness, vomiting and shortage of breath.

They were diagnosed as having been the victims of a poisoned gas attack allegedly unleashed by militants from the Islamic State group.

Iraqi forces said two other crude chlorine gas attacks have occurred since the summer, but the Post said the details were unclear.

"No, I am not in a position to confirm" the report, Kerry told reporters after meeting with his South Korean counterpart Yun Byung-se.

"We are seeking additional information in order to be able to determine whether or not we can confirm it," he added.

"The use of any chemical weapons is an abhorrent act, it's against international law, and these recent allegations underscore the importance of the work that we are currently engaged in."

But the top US diplomat stressed the reports would not change the US strategy as it builds a coalition to fight IS militants who have seized control of a large area of Iraq and Syria.

It might affect "tactical decisions" taken as part of the strategy, but the US is "step-by-step bringing the coalition further down the road to being able to shore up the Iraqi army itself and to take measures against ISIL," Kerry said, using another acronym by which the group is known.