Iraqi forces arrest Sunni Arab politician's son

The separate pre-dawn raid in Diyala province highlighted the tension in one of the country's most violent regions. Governor Raad Rasheed Mulla Jawad, who survived a bomb attack last week, said a counter-terrorism unit stormed his office in the provincial capital Baquba at 2:30 a.m. (1:30 p.m. British time).

They killed the governor's secretary, Abbas Ali Hmoud, and arrested senior provincial council member Hussein al-Zubaidy and the dean of the local university. Four policemen were wounded in clashes that followed between the raiding party and other units.

The provincial council announced it was suspending all work until it received an explanation for the assault. The governor called for a three-day period of mourning for his secretary.

"The body of the martyr will stay in the building until the killers are captured," the governor told Reuters. He was not present in the building during the raid.

Authorities offered no official account of who was behind the raid or its purpose. The men who conducted it arrived in military vehicles and wore uniforms but were not identifiable.

The U.S. military said it was not alerted in advance and could offer no further explanation.

Diyala, an ethnically and religiously mixed province in a fertile area north of Baghdad, has remained one of the most violent parts of Iraq even as the rest of the country has become safer over the past year.

U.S.-backed Iraqi forces launched a crackdown last month on Sunni Arab militants believed to be hiding out in its lush palm groves. The Americans and their Iraqi allies have also battled militias that they say have infiltrated the police.

Diyala's latest tensions appear linked to the firing of a police chief by the provincial council, days before last week's failed bomb attack on the governor. The issue has led to street protests.

(Additional reporting by Aws Qusay and Ahmed Rasheed, editing by Mark Trevelyan)