Iraq has meanwhile reported an attack by US warplanes on a civilian airport in Basra.

"American crows [planes] launched...on Wednesday night a new aggression when they attacked Basra international airport," said an official statement quoted on Iraqi television.

"The raids led to destroying the main radar system in the airport as well damaging the main service building."

A Pentagon official in Washington confirmed that there had been a strike early on Thursday, but gave no further details.

The US and Britain have enforced air exclusion zones since the 1991 Gulf War to protect Kurds in northern Iraq and Shiites in the south.

Air strikes have increased in recent weeks as the US steps up efforts to win international support for possible military action to overthrow the government in Baghdad.