Iraq's caretaker Prime Minister Adel Abdul-Mahdi said on Wednesday that Iran had notified Baghdad before striking U.S. bases in the country.
"At midnight, we received an official verbal notice from the Islamic Republic of Iran that their retaliation over assassination of martyr Qasim Soleimani had started or will start shortly," said a statement from his office.
Iraq was informed that the Iranian targets will be limited to locations where U.S. troops are stationed, it added.
Early on Wednesday, Iran's Revolutionary Guards Corps launched more than a dozen ballistic missiles against U.S. military and coalition forces in Iraq.
This comes after the Iraqi parliament voted on Sunday to expel American troops from the country while the U.S. President Donald Trump refused to do so threatening Baghdad with sanctions.
Tensions are high in the region after a U.S. drone strike last week killed a top Iranian general, Qasem Soleimani in Iraq.
Following the Iranian strikes, Iran's Foreign minister Mohammad Javid Zarif confirmed that Iran took the measure in self-defense and did not seek to escalate the confrontation.