Planes dropped 40,000lb (18,100kg) of explosives during a 10-minute blitz on 40 targets, according to a military statement.

The attack, involving B-1 bombers and F-16 fighters, was part of operation Phantom Phoenix, a campaign launched on Tuesday against al-Qaida insurgents who have regrouped following the "surge" around Baghdad.

"Thirty-eight bombs were dropped within the first 10 minutes, with a total tonnage of 40,000 pounds," the statement said.

Last night, the US military announced that nine US soldiers were killed in two attacks in the first two days of Phantom Phoenix.

The attacks came as militants fled American and Iraqi forces massing in Diyala, a province that has failed to experience the decline in violence that has happened in other parts of the country since the "surge" of US troops.

Six soldiers were killed and four wounded in a booby-trapped house in Diyala, while three soldiers were killed and two wounded in an attack on Tuesday in Salahuddin province, north of Diyala.

Major General Mark Hertling, the commander of US forces in northern Iraq, said that in his area - Diyala, Salahuddin, Kirkuk and Nineveh provinces - 24,000 US troops, 50,000 Iraq troops and 80,000 Iraqi police were fighting.

His presentation appeared to be designed to reinforce a message that the US mission had brought some success, helped by mounting Iraqi resistance to al-Qaida by the Sahwa (Awakening) movement.