Baghdad Governor Ali al-Haidri has been shot dead in a roadside ambush in the Iraqi capital, the highest-profile assassination there since May.
Ali al-Haidri had survived a previous assassination bid
Gunmen fired on his armoured-plated car from different directions as his convoy drove through northern Baghdad.
Violence has been escalating in Iraq ahead of elections on 30 January.
In separate incidents, 10 people were killed in a blast in the capital while attacks across the country claimed the lives of five US soldiers.
Mr Haidri is the most senior Iraqi official to be assassinated in Baghdad since the head of the Governing Council was killed by a suicide bomb in May last year.
At least one of his bodyguards was also killed in the attack, in the Hurriyah district on the west bank of the Tigris river.
3 January 2005: More than 20 people killed in a day of violence across Iraq
2 January 2005: At least 23 Iraqi soldiers killed by a car bomb in Balad
27 December 2004: 13 die in a Baghdad car bomb targeting a top Shia political leader
21 December 2004: Suicide blast in a US military base in Mosul kills 22 people
19 December 2004: More than 60 die in twin suicide car attacks in Najaf and Karbala
Iraqi insurgents have repeatedly targeted government officials around the country.
Mr Haidri escaped assassination in a roadside bomb attack in September.
In Thailand, US Secretary of State Colin Powell expressed regret at Tuesday's assassination, but said Iraq's elections would go ahead.
Mr Haidri's assassination took place hours after a suicide bomber rammed a fuel truck into a checkpoint near Baghdad's Green Zone, the heavily fortified government and diplomatic compound.
The explosion shook the city and turned the immediate area into an inferno, says the BBC's Jim Muir in Baghdad.
Eight members of an elite commando unit are said to be among the 10 people killed. About 60 others were injured in the attack, near an Iraqi special forces command post.
Also on Tuesday, a roadside bomb attack killed three American soldiers in Baghdad, the US military said.
Another soldier was killed in a bomb blast in Balad, north of the capital, and a US marine died in western Iraq's restive Anbar province.
Three Iraq national guardsmen are also reported to have been killed near Baquba, north of the capital.
The most recent attacks come a day after at least 20 people were killed across the country.
Meanwhile, Iraqi interim President Ghazi Yawer has joined several Sunni leaders in calling for a postponement of this month's polls.
Many top Iraqi officials privately favour a delay until the violence is quelled but they are unwilling to challenge the US, says our correspondent.