The assassination is the latest in a spate of deadly attacks ahead of elections scheduled for 30 January. Insurgents have repeatedly targeted Iraqi government officials around the country, calling them collaborators with the U.S.-led coalition.
Al-Haydari is the highest-ranking Iraqi official to be killed since the assassination last May of the president of the now defunct Iraqi Governing Council, Abd al-Zahra Uthman Muhammad, better known as Izzadine Salim.
Kathleen Ridolfo, an Iraq analyst for RFE/RL, describes al-Haydari as a well-known and respected politician. She says his high public profile made him a likely target for insurgents. "Today's killing of al-Haydari should be seen in the context of the recent surge in violence ahead of January's elections," she said. "We had four bombings in Iraq yesterday in various parts of the country. We're going to see things like this across the country until the end of the month. The goal of the insurgents right now is to intimidate the voters to keep them from going to the polls. And also to send a message to the leaders and the politicians who are running in the election that they can be targeted, [that] no one is away from their reach."
The U.S. government reacted quickly to the news. In Thailand, U.S. Secretary of State Colin Powell called al-Haydari's murder a clear attempt to derail the elections: "It once again shows that there are these murderers and terrorists, former regime elements in Iraq that don't want to see an election. They don't want to see the people of Iraq choose their own leadership. They want to go back to the past. They want to go back to the tyranny of the Saddam Hussein regime. And that's not going to happen."
Powell expressed sorrow over the killing. But he said Iraq's elections will go ahead as scheduled on 30 January: "The Iraqi interim government is determined to fight this insurgency. And you can be sure the coalition will do everything it can to fight the insurgency so that the Iraqi people can have a successful election at the end of the month."
"Today's killing of al-Haydari should be seen in the context of the recent surge in violence ahead of January's elections."
Al-Haydari was an appointed technocrat who had worked closely with the United States on efforts to reconstruct the Iraqi capital. He had signed contracts worth hundreds of millions of dollars for international companies to rehabilitate municipal services in Baghdad, such as water, sewage, and electricity.
Last month, he defended Baghdad's relatively large amount of reconstruction expenditures compared with other Iraqi cities: "As regards Baghdad, it is possible to say that it has more importance and a larger budget than other cities. It is true that all of Iraq and its towns need more resources. But it is important to keep in mind the importance of Baghdad."
Al-Haydari told reporters a week ago that insurgent attacks and chronic insecurity are impeding reconstruction efforts in Baghdad. And he predicted a spike in violence in Baghdad ahead of the elections.
Al-Haydari survived an assassination attempt in September that killed two of his bodyguards.
In November, Baghdad Deputy Governor Hatim Kamil was killed by gunmen in an attack that was similar to today's ambush. The militant group Ansar al-Sunnah Army claimed responsibility for Kamil's death. His murder came on the day that voter registration began for the 30 January election.
A week ago (27 December), a suicide bomber targeted the Baghdad offices of the leading Shi'a political party -- the Supreme Council of the Islamic Revolution in Iraq (SCIRI). Thirteen people were killed outside the compound, but SCIRI leader Abd al-Aziz al-Hakim escaped uninjured.
Iraqi officials described that attack as a failed assassination attempt against al-Hakim. SCIRI's previous leader, Ayatollah Muhammad Baqr al-Hakim, was killed in a car bombing in Al-Najaf in August 2003.
Over the past four months there have been failed assassination attempts in Iraq against a number of top officials, including the head of the Iraqi National Congress, Ahmad Chalabi; Iraqi interim ministers; Kirkuk's Kurdish governor; and a former Iraqi interim national security adviser.
For a list of attacks against Iraqi political figures, see: Recent Attacks On Political Figures In Iraq
(RFE/RL Online and RFE/RL's Iraqi Service contributed to this report.)