Two British Muslim pilgrims killed alongside an Iraqi man by gunmen near Baghdad have been named.
The pilgrims were travelling to holy sites when they were attacked
They were Londoners Saifuddin Makai, 39, from Streatham, and Husain Mohammedali, 50, from Harrow, their mosque in Northolt, west London, said.
The men were attacked with three other British Shia Muslims and another Iraqi in a minibus going to Baghdad airport.
Meanwhile, hostage experts are hunting for a Briton abducted in Baghdad with three other westerners on Saturday.
A multi-national hostage team is trying to find Norman Kember, a retired professor in his 70s from London, who is an aid worker in Iraq.
The Britons, who had been on a tour of Shia holy places, were shot when their minibus neared a checkpoint in the Dora neighbourhood, Police Captain Talib Thamir told Associated Press.
The Husaini Mosque in London said Mr Makai left behind two sons and a daughter, while Mr Mohammedali had three daughters and a son.
"Everybody, upon hearing, has just left their jobs and whatever they were doing and come and gathered together to support one and other and support the families who have been affected," Mosque trustee Shabbir Abidali told BBC News.
The Mosque named the two British men and one British woman injured as Yahya Gulamali, who was shot in the back, and Ali Quaiyoom and Ms Zehra Jafferji.
All three were taken to Baghdad's Yarmouk hospital where Mr Gulamali has been operated on by doctors for stomach and spinal injuries.
Mr Qauiyoom and Ms Jafferji have been transferred to Baghdad's Green Zone for treatment.
The Dawoodi Bohra Community in west London told the BBC the two men killed belonged to its community.
They were said to be Asians of African origin who settled in Britain 30 years ago.
Survivor Zara Jafferti said the group had been in Iraq for five days
One of the survivors of the attack told BBC correspondent Caroline Hawley that as they travelled on a dual carriageway at about 40kmh, he heard what sounded like fireworks.
He said all the glass in the minibus shattered as they were shot at for about one minute.
They were heading to Baghdad airport for a flight to Dubai and eventually London.
Another survivor, Zara Jafferti, told reporters they had been in Iraq for five days, visiting the holy sites.
"We were just coming and all of a sudden we saw the shots. I immediately got down, and I don't know what I saw.
"I couldn't see anything. It was a fire."
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."
Foreign Secretary Jack Straw said the government's advice was that UK citizens should not travel to Iraq.
"The only exceptions are where they are subject to proper security protection. That is clear, it's explicit.
"We hope British citizens will follow it, but we have no way of obliging British citizens to do so," Mr Straw added.
Pilgrims to the area visit the tomb of Hussein, a grandson of the Prophet Muhammed, in Karbala and another site in Najaf, said general secretary of the Muslim Council of Britain, Sir Iqbal Sacranie.
Between 5,000 and 10,000 mainly Shia community members make the pilgrimage from Britain every year, he added.