United States officials say there's been another military incident involving Iraq -- this time over the south of the country.

The officials say Iraq opened fire on British aircraft patrolling the southern air exclusion zone.

US planes retaliated, firing missiles and laser-guided bombs on an Iraqi missile site.

All the aircraft returned safely to base.

There's been no word from Iraq.

It's the second clash this week -- there was an incident between US and Iraqi forces over northern Iraq on Monday.

Iraq insists that the British and American patrols are a viol;ation of its territory and it has said it will take action against them.