US forces had earlier confirmed capturing six suspects in an overnight operation in the area of the northern city of Arbil, in a raid which Iraqi and Iranian officials said was directed against the consulate building.

Washington has not confirmed that diplomats were targeted, but has long accused Tehran's agents of fomenting unrest in Iraq and smuggling weapons to militias involved in sectarian violence and attacks on US forces.

"The presidency and the government of the Kurdish region of Iraq express their disapproval of the operation against the Iranian consulate," a statement from regional president Massud Barzani's office said.

The statement recalled that diplomatic premises were protected from attack under international protocols and accused US forces of "damaging efforts to restore stability and security in Iraq."

"It would have been more appropriate to have notified government security forces in the province before taking any decision or any action against anyone in the province," the statement added.

Barzani's text went on to say that the entire Kurdish people rejected the US action and warned the United States not to allow its disputes with Iran to influence its actions in neighbouring Iraq.