A roadside bomb detonated Wednesday near a convoy of four-wheel drive vehicles usually used by foreign contractors in Iraq's southern city of Basra, an Interior Ministry source said.

"An improvised explosion device detonated at about 9:00 a.m. (0500 GMT) and hit a convoy of sport utility vehicles (SUV), destroying an SUV and killing four civilian Britons on the busy highway of Gzaiyza," the source told Xinhua on condition of anonymity.

A white four-wheel drive vehicle was overturned on a railroad after it fell from the highway by the powerful blast, the source quoted Basra police reports as saying.

However, a British embassy spokeswoman in Baghdad denied any casualties among British diplomats and military personnel in Basra, some 550 km south of Baghdad.

"No British national involved in the incident this morning in Basra," the spokeswoman told Xinhua without elaboration.

Source: Xinhua