Iraq has accused Iranian forces of entering Iraqi territory and shelling Kurdish rebel positions in the north.
Iranian troops bombed border areas near the town of Hajj Umran before crossing into Iraq, the defence ministry in Baghdad said on Sunday.
It said the Iranians targeted the PKK, a Kurdish group that has waged a 15-year insurgency against Turkey.
The PKK is believed to have links with anti-Iranian Kurdish fighters. There are no details on casualties.
The Iraqi defence ministry also says Iran launched a similar attack on Kurdish rebel positions in the same area on 21 April.
There are no reported comments from Tehran on either of the alleged incidents.