Four contractors killed in Basra

The explosion threw the contractors' vehicle from the road

Four US security contractors have been killed by a roadside bomb in the southern Iraqi city of Basra.

Officials said the men worked at the US consulate and were attacked on their way from the airport to central Basra.

TV pictures showed an overturned vehicle near a busy road. Three of the victims died instantly and a fourth died later in hospital.

The British military said its forces were securing the area, and an investigation had started.

Eyewitnesses said a convoy of four all-terrain vehicles was driving along the road when the attack happened.

"A roadside bomb blew up the last car and it flew over from one side of the road to the other," one witness said.

Roadside bombings have been relatively rare around Basra in recent months.

But two British soldiers died on Monday in a similar attack west of the city and two British security contractors were killed in late July.