Baghdad - Iraqi police arrested eight suspects on Tuesday in search of accomplices of a female suicide bomber who killed 22 people, security sources said.

The bomber blew herself up Monday amidst a crowd near a police station in Balad Ruz in Diyala province, 57 kilometres north-east of Baghdad, the Voices of Iraq (VOI) news agency reported.

Eleven policemen were among the 22 fatalities. Thirty-three civilians were injured in the attack.

According to a report by the Monitor of Constitutional Freedom and Bill of Rights, a Baghdad-based group, women embittered by the loss of their husbands and children in acts of violence are potential suicide bombers.

Baghdad - US Defence Secretary Robert Gates arrived in the Iraqi capital Baghdad on Monday on the eve of a shift in command of the US-led forces.

US General David Petraeus is spending his last day in Iraq on Monday as commander of US-led forces.

In a ceremony that will be held today, and attended by Gates, Petraeus will hand command to his former deputy Lieutenant-General Ray Odierno.

Odierno served as Petraeus right hand for 15 months until February. He will be promoted to full general on Tuesday.

Baghdad - The row over the role of Kurdish fighters, or peshmerga, in Iraq came to a head Monday, as officials warned them against operating outside the country's northern Kurdish Autonomous Region.

"If the peshmerga are deployed outside the Kurdish Autonomous Region, it is unconstitutional," said Abdel Karim al-Samarrai, the acting head of the Iraqi parliament's security committee.

The presence of peshmerga in the city of Khanakin, which lies in the province of Diyala, has caused friction, according to a statement from al-Samarrai posted on the website of his party, the Sunni Iraqi Accord Front.

Baghdad - Iraqi Prime Minister Nuri al-Maliki ordered an investigation Sunday into the killing of four journalists, according to a cabinet statement.

Those who committed this crime must be brought to justice to receive the just punishment they deserve, the statement said.

The journalists worked for Iraqi TV station al-Sharqia.

Unknown gunmen kidnapped them on Saturday in western Mosul, 405 kilometres north of Baghdad, the Voices of Iraq (VOI) news agency reported.

Baghdad - Seven policem

Baghdad - Six Kurdish peshmerga (militia) members were killed and three wounded as a bomb exploded on Saturday east of the disputed town of Khanaqin in northern Iraq as their patrol was passing, a security official said.

The relatively calm town, 57 kilometres north-east of Baghdad, came into the limelight in August following the deployment of mainstream Iraqi forces into the district claimed by Kurds.

Although it lies outside the Kurdish autonomous region, Khanaqin is inhabited mainly by Kurds.