Four US security guards were killed Wednesday in a roadside bomb blast near a convoy of foreign contractors in Iraq's southern city of Basra, a US embassy spokesman said.
"All four individuals worked for a private security firm supporting the regional US embassy office in Basra," the spokesman said in a statement.
Three of the victims were killed immediately by the blast and the fourth died after the British troops evacuated him to a military hospital.
Earlier, an Iraqi Interior Ministry source said the blast killed four civilian Britons.
"An improvised explosion device detonated at about 9:00 a.m. (0500 GMT) and hit a convoy of sports utility vehicles (SUV), destroying a SUV and killing four civilian Britons on the busy highway of Gzaiyza," the source told Xinhua, quoting 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.