United Nations Secretary General Kofi Annan has stressed the importance of national reconciliation in Iraq during a surprise visit to Baghdad.
Security has been stepped up during Mr Annan's visit
He arrived as the latest car bombing killed at least four people and injured 19 in an attack near a market.
Iraq's US-backed interim government is battling a mainly Sunni insurgency that has killed thousands of people.
The death of Saddam Hussein's fugitive right-hand man has been welcomed by Iraq's government as a blow to terror.
Prime Minister Ibrahim al-Jaafari said news of the death of Izzat Ibrahim al-Douri would have "a positive effect on Iraqis and a negative effect on terrorism".
Douri, 63, was the most senior figure from the ousted regime still at large and there had been a $10m US reward for information leading to his capture.
He is believed to have been suffering from cancer and the former ruling Baath party said he had died of natural causes, in a website announcement which could not be independently confirmed.
"Struggler comrade Izzat Ibrahim... passed away at dawn [on Friday] on the pure Arab land of Iraq," the statement said.
Message for Sunnis
Mr Annan had talks with Prime Minister Jaafari and other leaders in Baghdad ahead of next month's planned general election that will replace the transitional government.
"The idea is that reconciliation is absolutely essential in Iraq," Mr Annan said at a joint news conference with Mr Jaafari.
The car bomb exploded at a busy vegetable market
"I don't think anyone would argue with that."
Mr Annan backed an Arab League reconciliation initiative which begins with a conference in Cairo in a week's time and also envisages a broad-based peace conference for Iraq in January.
Mr Annan also met a Sunni delegation.
His message, the BBC's Jim Muir reports from Baghdad, is that the outside world fully supports the Iraqi political process and really wants the Sunnis to get on board, isolating the hardcore of the Sunni-based insurgency.
Mr Annan's visit to Iraq - his first since the US-led invasion in 2003 - follows separate trips by UK Foreign Secretary Jack Straw and US Secretary of State Condoleezza Rice.
The UN pulled out of Iraq after a bomb at UN headquarters in Baghdad in August 2003 killed 22 people, including envoy Sergio Vieira de Mello.
Mr Annan paid tribute to the dead on a visit to the UN compound.
"I have been wanting to come for quite some time," he told reporters.
"Our dear friends who died here in 2003... carried no guns, they came to help and their lives were cut short."
The latest car bomb attack took place in the south-eastern New Baghdad area.
Eyewitnesses said the explosion sparked fires in several shops in the busy market, trapping people inside.