Three military policemen, believed to be Polish, were killed in a grenade attack in the southern Iraqi city of Karbala, Iraqi police.
Policemen who were at the scene said a fellow policeman was also killed in a subsequent battle on Thursday night with the unidentified attackers.
They said the attack on a military police patrol occurred in the Bab Tweirij district of the Shiite Muslim shrine city, where rivalries among Shiite factions have led to bloodshed in recent weeks.
Polish forces lead an international brigade responsible for postwar security in the Karbala area.
The Iraqi policemen said they saw a red-and-white flag - apparently the Polish flag – at the scene of the attack.