A British soldier has been killed and four were seriously injured in a roadside bomb attack in Basra, southern Iraq, the Ministry of Defence has said.
The killing brings the total death toll for UK soldiers in Iraq to 98
The attack happened at about 1230 local time near the old port and citadel in the heart of Basra, Iraqi police said.
The MoD has launched an investigation into the attack but officials would not comment on the extent of the four soldiers' injuries.
The latest killing brings the death toll for UK soldiers in Iraq to 98.
Basra police sources said one of two vehicles on patrol was heavily damaged when it took a direct hit when the bomb went off.
Army spokesman Major Steve Melbourne said: "The incident is under investigation.
"The only thing we can actually confirm is that it was a road bomb. What make or anything else we are unable to ascertain at this particular time."
When asked whether insurgents could have been behind the attack, Maj Melbourne said: "We don't really have the problem with insurgents. It is more the terrorist element.
"These are very small groups that operate in the area. They cause serious risk to both ourselves and the local population of Basra."
He added: "Everybody is aware of how dangerous it is...[but] we will continue to do the job in a professional manner."
The BBC's Paul Wood said the device was likely to be one of a new type of explosive device which has killed British soldiers since August.
The new type of devices had sophisticated triggers and were capable of piercing through armour, which means patrols in southern Iraq were "far more risky" for British soldiers.
British officials have accused Iran of allowing the new technology to flow across the border to hostile elements - a charge the Iranians have strongly denied, BBC correspondent Jim Muir added.