The savage attack -- part of the sustained insurgent assaults on security forces in a bid to thwart US and Iraqi efforts to stabilise the war-torn country -- was the second of its kind in as many days.

The bomber detonated the vehicle against a police department building in an area called Albu Ajil, east of Tikrit, on the main road between the city and the oil hub of Kirkuk, police officials said.

At least 40 people, many of them policemen, were also wounded in the attack that took place at 10:15 am (0615 GMT), they said.

"Nine policeman have died in the blast and 40 more are wounded, mostly policemen," Major Abdul Karim Mohammed, a security official at Tikrit general hospital, told AFP.

Following the blast, Tikrit police announced on loudspeakers an indefinite curfew in the city, an AFP reporter said.

The attack came a day after a suicide bomber exploded his truck at an Iraqi army base near the town of Iskandiriyah, southwest of Baghdad, killing 14 soldiers and wounding 30.

Car bombs were also reported in Baghdad and the restive province of Diyala on Sunday.

Iraqi security officials said two people were killed and seven wounded as a car bomb exploded near a petrol station in Baghdad's Al-Bayaa district and one person died when another car bomb targeted a gas station in the Saidiyah area of the capital. Five people were also wounded in the Saidiyah attack.

In the town of Khan Beni Saad in Diyala, northeast of Baghdad, a car bomb killed a policeman and wounded three people, police Lieutenant Ahmed Ali said from Baquba.

He said the bomb targeted a police checkpoint.

Also on Sunday, a Kurdish officer serving in the Iraqi army was killed and two of his colleagues were wounded when their vehicle struck a roadside bomb near Sulaiman Bek, said Abbas Mohammed Amin, police chief of the nearby town of Tuz Khurmatu.

The three officers were deployed in Baghdad as part of the ongoing "surge" in the Iraqi capital and were on their way back home when the bomb hit their vehicle, he said.

US and Iraqi forces are currently carrying out a massive security operation in Baghdad to curb sectarian violence unleashed since early last year.

The surge, announced by US President George W. Bush, is expected to see 160,000 US troops deployed in Iraq, mostly in Baghdad, by the end of this month.

A Washington Post report on Sunday said the United States is considering a long-term military presence in Iraq that will not have the scope of the current occupation but still be capable of mounting independent operations.

Citing US military officers and other unnamed officials, it said the plan is based on assessments that a sharp drawdown of troops is likely to begin by the middle of next year, with roughly two-thirds of the current force of 150,000 moving out by late 2008 or early 2009.

An al-Qaeda linked Iraqi militant group on Sunday claimed responsibility for the killing of a female journalist in the northern city of Mosul, in an Internet statement.

Militants from Ansar al-Sunnah shot dead Sahar al-Haydari, 45, who worked for the Voices of Iraq news agency, "for distorting the image of the Mujahedeen (holy warriors)", the group said.

Police have said Haydari was killed on Thursday in the Al-Habdaa district of the city as she was on her way to work.

According to a June 6 toll posted by Reporters without Borders on their website, 182 journalists and media workers, mostly Iraqis, had been killed in Iraq since the US-led invasion of March 2003.