Diplomat Thamer al-Sabhan had called for the exclusion of Shia paramilitary units from Iraq’s campaign against ISIL.
Five attackers armed with suicide vests, rifles and grenades have killed 18 people in the Iraqi town of Ain al-Tamer, southwest of Baghdad, local officials say.
A member of the local council and a source at the provincial health directorate confirmed the death toll in the attack, which occurred late on Sunday, and said at least 26 people were also wounded.
Officials said the attackers opened fire in a neighbourhood of Ain al-Tamer at around 18:30 GMT on Sunday, although it was not immediately clear what their target was.
“They were carrying Kalashnikovs and hand grenades. One of them blew himself up and the others were killed by the security forces,” Qais Khalaf, the head of the central Euphrates operations command, said.
Five members of the same family were among the dead, according to a health official from Karbala province.
The Islamic State of Iraq and the Levant (ISIL) group has claimed responsibility for the attack.
Ain al-Tamer lies about 50km west of the holy city of Karbala.
The bombing is the first in the Karbala region since Iraqi forces dislodged ISIL fighters from their stronghold in Fallujah, 80km north of city.