Four more British soldier have been killed by an improvised explosive device on the Shatt Al Arab waterway near Basra.
British military spokesmen said the men were hit by an IED on the banks of the waterway while they were in a patrol boat, three others seriously wounded.
According to the spokesman, at least one of the injured had sustained potentially life-threatening wounds.
The British have been patrolling the waterway, which borders with Iran and is considered a vital supply line, since 2003.
The attack took place at 9.50 GMT.
Meanwhile in a separate incident, the US military says three American soldiers have been killed in combat while operating in western Al-Anbar province.