The planes dropped laser-guided bombs on Iraqi anti-aircraft and command-and-control sites in self defence, according to US Air Force officials. All the planes involved are reported to have returned safely to base.

The Iraqi military claimed US and British warplanes attacked a civilian installation, injuring one person, according to the official Iraqi News Agency.

US and British planes patrolling air-exclusion zones over northern and southern Iraq have fired on Iraqi forces on the ground several times a week since December, when the allies carried out four days of intensive bombing.

Iraqi forces use radar, artillery and missile fire to challenge the US and British air patrols, provoking retaliatory attacks.

This was the third time in a week that targets near the Iraqi city of Mosul were hit by American planes.

Iraqi officials said a strike on Sunday in the south of the country killed four people.

Iraq does not recognise the legitimacy of either of the air exclusion zones, which are not covered by a specific United Nations resolution.

Monitoring in tatters

But the US and Britain argue that they are empowered to act by more general resolutions passed after the Gulf War in 1991.

International attention has drifted away from the Iraqi crisis since the Nato air campaign against Yugoslavia began in March but the low-level military conflict continues alongside a political stalemate.