The announcement was timed partly to shore up public sentiment in favor of the elections Sunday, reports CBS News Anchor Dan Rather from Iraq.
Insurgents, meanwhile, targeted more polling sites across the country, and a suicide car bomber killed four policemen in the capital. U.S. fighter jets thundered through the skies over Baghdad throughout the morning in a show of force against the militants.
American troops and insurgents exchanged fire on a major Baghdad thoroughfare. The crackle of gunfire could be heard over the noon call to prayer.
Qassim Dawoud, a top security adviser, told reporters that the arrests of the al-Zarqawi lieutenants occurred in mid-January but gave few details. Dawoud said one of the men, Salah Suleiman al-Loheibi, headed al-Zarqawi's Baghdad operation and had met with the Jordanian-born terror leader more than 40 times over three months.
The other was identified as Ali Hamad Yassin al-Issawi.
The announcement brings to three the number of purported al-Zarqawi lieutenants arrested this month. The announcement appeared aimed at bolstering public confidence in security forces in advance of Sunday's election.
In other developments:
Iraqis will choose a 275-member National Assembly and governing councils in the country's 18 provinces.
Rebels have threatened to kill anyone who votes, and officials fear a low turnout, especially among Sunni Arabs, could tarnish the legitimacy of the new government.
However, confidence is high among U.S. commanders in the field that with the exception of some of the worst parts of the Sunni triangle, the turnout will be larger than most people in America believe, Rather reports.
The U.S. ambassador in Baghdad, John Negroponte, also insisted some Sunnis will turn out to vote. "Sunnis don't only live in some of these beleaguered provinces, they live here in Baghdad, they live in other parts of the country," Negroponte said on CBS News' The Early Show. "I think you're going to see participation across the board."
On Thursday, al-Zarqawi's al Qaeda affiliate in Iraq posted a video on the Internet showing the murder of a candidate from Prime Minister Ayad Allawi's party. The tape included a warning to Allawi personally: "You traitor, wait for the angel of death."
Friday's suicide car bombing rattled Baghdad's Doura neighborhood, a flashpoint in recent days, with several street battles between insurgents and Iraqi National Guard troops, and with assassinations of government officials.
Police opened fire on the speeding car in an attempt to stop it just as it burst into flames. Hours later, another car bomb exploded on the neighborhood's main road, causing some damage to a school where voters are to cast ballots Sunday. No one was hurt.
Elsewhere, insurgents hit designated polling centers in at least six major cities across the country. Gunmen attacked a school to be used as a polling station in Kirkuk, killing one policeman, officials said.
Bombs blasted three more schools designated as polling sites in the city of Beiji, 155 miles north of Baghdad. A mortar shell landed on a house close to a school believed to be used as polling site in the western city of Ramadi, wounding two women and two children, a hospital doctor said.
In southern Iraq, a roadside bomb hit an Iraqi police vehicle, killing one officer and wounding three others, said police Lt. Col. Karim al-Zaydi. The attack occurred in the town of Zubair, south of the port city of Basra.
Also Friday, insurgents shelled a U.S. Marine base south of Baghdad, injuring three American troops and three civilians, the military said.
Authorities on Thursday night found the bodies of four Iraqi National Guardsmen who had been shot dead in Ramadi, capital of the troubled Anbar province. Police believe the four had been kidnapped several days ago.