A powerful car bomb has exploded in a busy square of the Iraqi capital, Baghdad, killing at least 12 people including foreign contractors.
Dozens were injured in neighbouring buildings
It went off as a convoy carrying contractors was passing through Tahrir Square, setting light to their 4X4 vehicles and destroying a building.
Two British, one US and one French employee of the US power company General Electric are among the dead.
Iraq's interim interior minister said the suicide bomber was a foreigner.
"The initial information shows that the person who carried out the bombing was not Iraqi and came from outside Iraq," Falah al-Naqib told al-Arabiya television.
"Most probably, [the perpetrator] came from a country not neighbouring Iraq."
Two private security guards were among the GE dead and 10 other contractors were injured, US officials said.
Iraq's interim Prime Minister, Iyad Allawi, described the blast as a "cowardly" attack on "people helping Iraq rebuild its power generating stations".
BBC Middle East analyst Roger Hardy says the attack is a grim reminder of the challenges ahead following last week's passage of a new UN resolution on Iraq, heralded by some as the beginning of a more hopeful chapter for the country.
US and Iraqi officials have warned of an increase in bloodshed in the country as it moves towards the handover of sovereignty on 30 June.
A UK Foreign Office spokesman did not reveal the names of the dead Britons but said next-of-kin were being informed.
It is not clear how many Iraqis were hit by the blast. Frantic passers-by scooped up the wounded and loaded them into private cars to be taken to hospital.
Maj Mohammed Saleh, the top policeman at the scene, told AFP news agency that a suicide car bomber in a small Volkswagen Brazilia had "driven between the cars and blown himself up".
But other witnesses said they thought a parked car was detonated by remote control.
Trapped under rubble
The explosion destroyed a building and left a huge crater surrounded by burnt-out, mangled cars.
Capt Issam Ali at the nearby Neurological Hospital said many of the injured had serious burns and had lost limbs.
Anger at the explosion quickly turned to fury at the US, as crowds began hitting the burnt-out cars and shouting "God is Great" and "Down with the USA".
There were reports that the crowd poured fuel over one of the destroyed vehicles and set it on fire.
US troops beat one man with a stick, but the troops and Iraqi police withdrew when they failed to restrain the crowd, Associated Press reported.
The attack on electricity contractors comes as the US-led Coalition Provisional Authority is struggling to fulfil a pledge to bring Iraq's electricity generating capacity to 6,000 megawatts before the handover of sovereignty.
The CPA stopped issuing daily figures in May when the peak output was a little over 4,000 megawatts.
A second car bomb was reported near the town of Salman Pak south-east of Baghdad. Police quoted by AP said a car drove between police vehicles and exploded, killing four people and injuring four others.
The blasts come a day after a suicide car bomber killed at least seven Iraqis outside a US base in the city, the latest in a spate of such attacks.