Investigations are continuing in the Iraqi capital of Baghdad after a lorry bomb exploded outside the Jordanian embassy, killing at least 17 people and injuring dozens.
The blast destroyed cars close to the embassy
US defence officials said that they were focusing attention on the radical Islamic group Ansar al-Islam, which the US accuses of links to Osama Bin Laden's al-Qaeda network.
"I think the one organisation that we have confidence that we know is in Iraq and in the Baghdad area, is Ansar al-Islam," senior US Defence Department official Lieutenant General Norton Schwartz told Reuters news agency.
However General Schwartz said that it was not known if the group had been involved in Thursday's attack.
No group has admitted carrying out the attack, but correspondents say that groups responsible for the regular attacks against US troops in Iraq are almost certainly behind this incident.
The death toll rose on Friday, when an official in charge of the morgue at a hospital near the embassy said two wounded Iraqi police officers had died overnight, and another four bodies had been found.
The force of the explosion sent a car hurtling onto a rooftop and left body parts and debris strewn across the street.
Jordanian officials said all the identified dead were Iraqis. The latest death toll is believe to include at least six police officers.
The attack comes a week after Jordan granted refuge to two of Saddam Hussein's daughters and their children, angering some Iraqis.
Witnesses outside the walled embassy compound said the bomb was concealed inside a minibus or sports utility vehicle. A Jordanian official said he thought a missile was fired at the vehicle to set off the explosives.
One witness said he saw the charred bodies of a woman and two children still sitting in one of the burned-out cars nearby.
Jordanian Information Minister Nabil al-Sharif condemned the attack as a "cowardly terrorist" act.
Elsewhere in Baghdad on Thursday, US troops were involved in a fierce gun battle with Iraqis after an American Humvee vehicle was destroyed in an attack. At least one Iraqi bystander was killed.
After the bomb, dozens of angry Iraqis stormed the building, smashing portraits of Jordan's King Abdullah II and his father King Hussein.
The crowd was quickly dispersed by US soldiers and Iraqi police.
A US army spokeswoman said two American soldiers were wounded.
On Wednesday night, two American soldiers died in a firefight in the al-Rashid district of Baghdad. It took to 55 the number of US troops killed by hostile fire since the US declared the war largely over on 1 May.
US Secretary of State Colin Powell has said US troops still had much to do bring the situation under control in Baghdad. He blamed Saddam Hussein loyalists and "some from the outside" for the unrest.
In past years Jordan has found itself caught in the middle of Iraq's relations with the West, says our Baghdad correspondent Matthew Price.
Many Iraqis believe Jordan took advantage of tough UN sanctions on Iraq, acquiring cheap oil from the oil-for-food programme, while offering tacit support to Saddam Hussein's regime.
Jordan supported the US-led war in Iraq, allowing the US to use its territory for military bases.
Iraqis also complain that Jordan has frequently been reluctant to offer asylum to ordinary members of the public.
Jordan is thus resented both by Iraqis who opposed Saddam's regime and those who supported it, our correspondent says.