Two Britons were killed and three injured when a gunman attacked a bus carrying Muslim pilgrims south of Baghdad.
The attack comes after it emerged today that a Briton in his 70s is among four people kidnapped in Baghdad on Saturday.
Professor Norman Kember from north west London was snatched alongside two Canadians and an American.
The Canadian authorities confirmed that two nationals had been kidnapped. The news has been met with shock in Canada particularly because the country opposed the US-led invasion of Iraq.
It is understood the four were part of an informal aid group operating in Baghdad. Prof Kember 's wife, Pat, said: "He is representing a number of different organisations."
The British Foreign Office would not confirm who Prof Kember was working for or the location where he was kidnapped. A spokeswoman said: "We will be in touch with the Iraqi authorities, and with the other countries involved, the Americans and the Canadians. We will be setting in motion an urgent investigation."
A representative of the group in Baghdad, who refused to be named, said they had received no word on their condition and had no information on the group that had seized them.
It is the first kidnapping of foreigners in Baghdad since an Irish journalist on an assignment in Iraq was kidnapped in October. The journalist, Rory Carroll, was released unharmed after 36 hours.
The two Britons killed today were killed en route to religious sites south of the capital when the bus they were in was attacked as it neared a checkpoint in the Dora neighbourhood.
The dead and injured - four men and one woman, apparently of South Asian heritage and carrying UK passports - were taken to Baghdad's Yarmouk hospital, an official said.
A Foreign Office spokesman said: "Our consular and security staff are investigating the reports. They have heard it could be two British nationals, but at this stage we know no more than that. The reports are being investigated."