A suicide car bomber rammed an explosives-laden vehicle against the wall of a police station near the northern city of Mosul on Thursday, killing three policemen and wounding four others, 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. The Thursday attack occurred at a police station in the Qayara area about 50 kilometers 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." US and Iraqi forces have been battling al-Qaida-inspired insurgents for months in Mosul, where militants have staged numerous car bombings and assassinations.