Iran's Islamic Revolutionary Guard Corps has said that seven Iranian military advisers died in the strike, including Mohammad Reza Zahedi, a senior commander in its Quds Force.
US strikes in the west of Iraq against armed pro-Iran groups killed at least 16 people, including civilians, and wounded 23, Iraqi government spokesman Bassem al-Awadi said on Saturday.
Iran's President Ebrahim Raisi said on Friday that his country would not start a war but that it would "respond strongly" to anyone who tried to bully it.
The US administration has approved plans for multi-day strikes in Iraq and Syria on targets including "Iranian personnel and facilities", CBS News reported on Thursday, citing American officials.