BAGHDAD — A suicide car bomber rammed an explosives-laden vehicle into the wall of a police station near the northern city of Mosul on Thursday, killing three policemen and wounding four, police said.

It was the fifth suicide attack in Iraq this week and shows that insurgents can still carry out assaults despite security gains in urban areas. Four suicide bombers killed 57 people in Baghdad and the northern city of Kirkuk on Monday.

President Bush declared progress in the Iraq war Thursday, saying terrorists "are on the run" and a generally improved security environment should permit further U.S. troop reductions.

The attack on the police station happened in the Qayara area about 30 miles south of Mosul, according to a police officer who spoke on condition of anonymity because he was not authorized to speak to the media.

A statement posted Wednesday on a Web site in the name of the Islamic State of Iraq, an al-Qaida front group, warned of a campaign of attacks in the Mosul area in retaliation for the killing of one of its "hero brothers."

On Thursday, a judge died of wounds suffered in an attack the day before in Mosul, police said. One of the judge's bodyguards was killed in the attack, police said.

U.S. and Iraqi forces have been battling al-Qaida-inspired insurgents for months in Mosul, where militants have staged numerous car bombings and assassinations.

The focus of the war against al-Qaida and other Sunni militant groups has shifted to the north after the Sunni revolt against the terror movement in Anbar province west of Baghdad. Sunni militants have also suffered major losses in the Baghdad area since 2006.

About 50,000 U.S.-backed Iraqi military and police forces have launched a major operation against al-Qaida insurgents in Diyala province northwest of the capital. Iraqi officials have described Diyala as one of the last major al-Qaida strongholds near the capital.

Insurgents on Thursday clashed with U.S.-allied Sunni Arab fighters and killed one of them near the village of al-Waib, south of the provincial capital of Baqouba. The insurgents also wounded another fighter and a villager before escaping in a convoy, police said.

Iraqi forces on Thursday arrested 12 policemen on suspicion of collaborating with the insurgents near Baqouba, the police said.

AP Television News footage on Thursday showed Iraqi troops transferring a handful of detainees in the back of a truck in Diyala. One of the soldiers was seen feeding a a slice of orange to a blindfolded captive as others gave them water.

Also Thursday, the U.S. military said American soldiers wounded a civilian woman after opening fire on a group of four suspected militants during an operation in Samarra, north of Baghdad.

The military said another woman was also killed in the confrontation but her status had not been determined.

In Baghdad, a bomb blast wounded three civilians in central Baghdad on Thursday, police said.