TEHRAN - Iran has said the United States showed its "support for terrorism" by carrying out air attacks on the Shia armed group Kataib Hezbollah in Iraq and Syria.

The Pentagon said on Sunday that it had targeted the Iran-linked militia group in western Iraq and eastern Syria in response to the killing of a US civilian contractor two days earlier.

Iraqi security and militia sources said at least 25 fighters had been killed and 55 others wounded in the air attacks in Iraq which the US described as "defensive strikes".

At least four Kataib Hezbollah commanders were among the dead, the sources said, adding that one of the raids had hit the Iran-backed group's headquarters near the western al-Qaim district on the border with Syria.

"These attacks have once again proved America's false claims in fighting Daesh... as the United States has targeted the positions of forces that over the years have inflicted heavy blows to Daesh terrorists," Iran's government spokesman Abbas Mousavi said, referring to ISIL (ISIS).

"With these attacks, America has shown its firm support for terrorism and its neglect for the independence and sovereignty of countries and it must accept consequences for its illegal act," he said in a statement.

The spokesman said the presence of foreign forces in the region was the cause of insecurity and tensions. "America must put an end to its occupying presence," said Mousavi.

US-Iran tensions have soared since Washington pulled out of a landmark nuclear agreement with Tehran last year and began reimposing crippling sanctions.(FA)