The current head of Iraq's US-appointed Governing Council has been killed in a car bomb blast near the headquarters of the US-led coalition in Baghdad.
Salim is the most senior Iraqi to be killed
Ezzedine Salim was near a checkpoint outside the compound when the bomb went off, killing him and several others.
It is not yet clear whether Mr Salim was the target of the suicide attack.
A US military spokesman said it bore all the hallmarks of attacks carried out by supporters of Jordanian-born al-Qaeda suspect Abu Musab al-Zarqawi.
The US administrator for Iraq, Paul Bremer, condemned the killing and vowed to defeat those responsible.
"The terrorists who are seeking to destroy Iraq have struck a cruel blow with this vile act," Mr Bremer said in a statement.
But they would be defeated and Mr Salim's vision of a "democratic, free and prosperous Iraq" would become a reality, he said.
The IGC also condemned the killing of their leader.
Ghazi Ajil al-Yawer - a Sunni Muslim from the northern city of Mosul appointed as Mr Salim's successor - said he would continue the march towards freedom and democracy despite the bomb attack.
"This is a terrorist act that will not dissuade the Governing Council from continuing its work to build a federal, united Iraq," he said.
Mr Yawer will serve as IGC head until the transfer of sovereignty to Iraqis, scheduled for 30 June.
In other developments:
- Coalition troops found an artillery round containing the deadly nerve gas sarin, but were unable to defuse it and a small "dispersal of agent" occurred, the US military said.
- Coalition troops estimate they have killed 30 Moqtada Sadr militiamen in the holy city of Karbala.
- In the southern city of Nasiriya, one coalition soldier and about 20 militants were killed in overnight fighting.
- The US is planning to move some of its forces from South Korea to Iraq, South Korean officials say.
- Britain and the US have emphasised their intention to accelerate the training of the Iraqi army and police force to allow the earliest possible withdrawal of their troops.
The explosion in which Mr Salim was killed happened at 0500GMT at a checkpoint outside the Green Zone - the sealed-off area where the coalition and the IGC both have their offices.
Several vehicles were destroyed in the blast, which melted the asphalt of the road and sent debris flying over a large area.
"There was a huge crowd at the checkpoint," a security guard at a nearby residential compound told the Reuters news agency.
The blast at the IGC followed an attack on coalition HQ in January
"There were a lot of cars and people on foot standing there and then this massive explosion. I saw body parts everywhere."
A previously unknown Iraqi group said it had carried out the attack.
The Arab Resistance Movement al-Rashid Brigades posted a statement on the internet saying two suicide bombers had been used to carry out "a qualitative heroic operation, which led to the killing of the traitor and mercenary" Ezzedine Salim.
"The Brigades pledges to the masses of our nation to pursue struggle until the liberation of glorious Iraq and dear Palestine," the statement on al-Anbar website said.
US military spokesman Brig Gen Mark Kimmitt said they were investigating the statement of the group that could be a cover for the Zarqawi network.
Gen Kimmitt said the bombing that killed the IGC president had all the hallmarks of Zarqawi - the use of suicide bombers, going after spectacular and symbolic targets, and killing large numbers of civilians.
Mr Salim, a Shia Muslim and member of the Daawa Islamic Party, was the current holder of the rotating IGC presidency.
He is the second council member to be killed since it was set up last July.
IRAQI GOVERNING COUNCIL
Set up July 2003; due to be abolished at end of June
Members from Iraq's different religious, ethnic groups
Many members were exiles under Saddam Hussein
Presidency rotates monthly
Signed interim constitution in March
Aquila al-Hasimi, one of three women on the IGC, was shot dead last September.
International condemnation was also swift.
The killers of Ezzedine Salim are "enemies of the Iraqi people", British Foreign Secretary Jack Straw said on Monday in Brussels.
French President Jacques Chirac said he was "as convinced as ever that there is no military solution" in Iraq.