A suicide bomber killed sixteen policemen in Baghdad today, a day after the capital suffered its bloodiest day as US troops and insurgents clashed in the troubled western town of Ramadi.

US and Iraqi troops swept into the insurgent stronghold of Tal Afar early today, conducting house-to-house searches and battering down walls with armoured vehicles in a second bid to clean the city of militant fighters.

A co-ordinated string of four bomb attacks within seven minutes killed at least 18 people and wounded 39 in northern Iraq today, while a Baghdad car bomb injured 28, officials said, ending a relative lull in violence that had fallen over the country in recent days.