The seizure of Abu Umar al-Kurdi, alleged to be a senior aide to Abu Musab Al-Zarqawi, purported leader of al-Qaida Group in the Land of Two Rivers, appeared to be a major breakthrough for the authorities before next Sunday's election.
Abu Umar, also known as Sami Muhammea al-Jafi and accused of masterminding some of the worst car bombings in Iraq, was seized in a raid in Baghdad on 15 January, the government said.
He is blamed for more than 30 bombings, including the attack on the UN headquarters in August 2003 which killed special envoy Sergio Vieira de Mello and 20 others, as well as a blast in Najaf the same month which killed 80, including a leading Shia cleric.
"Kurdi has confessed to some 75% of the car bombs that were used for attacks in Baghdad since March 2003 and to making the explosives used in the attack on the Jordanian embassy in August 2003," government spokesman Thair al-Naqib said.
Both officials and voters fear a
massive assault on election day
The government said Abu Umar had received instructions from al-Zarqawi to carry out a series of bomb attacks on election day - precisely the sort of assault the government, opposition figures, voters and international observers fear.
Iraq's electoral commission has said 14 million of Iraq's 27 million people could go to the polls on Sunday, creating what the UN has described as the biggest security and organisational challenge since Saddam Hussein's fall.
The announcement of Abu Umar's arrest and that of another senior anti-US figure, Nayif Abbas al-Zubaydi, came hours after a car bomb struck near Allawi's party office in central Baghdad, injuring 10 people.
Al-Zarqawi's group claimed responsibility for the attack in a statement published on the internet. The statement could not be independently verified.