"It is with regret that I have to announce the death of two soldiers from the Queen's Royal Lancers operating a Challenger II main battle tank," a defence ministry spokesman told AFP.

"The soldiers were killed last night (Monday) in a friendly fire incident from another British Challenger during a period of multiple engagements with Iraqi enemy forces on the outskirts of Basra," he said.

The spokesman added: "Two other soldiers were seriously injured and have undergone surgery."

The latest deaths brings to 18 the number of British troops who have died as result of friendly fire since war began six days ago.

Two British troops have also died in combat and two are listed as missing.

WAR.WIRE