Authorities in Iraq have arrested three close associates of Abu Musab al-Zarqawi (search), officials said Friday, claiming to be close to capturing the Al Qaeda-linked terror mastermind himself two days ahead of historic elections that extremists have vowed to subvert.

The announcements, made days after the arrests, appeared aimed at helping reassure Iraqis about security ahead of Sunday's polls. Still, violence continued: Insurgents killed five U.S. soldiers, set off a homicide car bomb that killed four Iraqi policemen in Baghdad and targeted more polling sites across the country.

American troops and insurgents exchanged fire on a major Baghdad thoroughfare. The crackle of gunfire could be heard over the noon call to prayer. U.S. fighter jets thundered through the skies over Baghdad throughout the morning in a show of force against the militants.

A U.S. Army OH-58 Kiowa (search) helicopter crashed in southwest Baghdad on Friday night, and the fate of the crew was not immediately known, a U.S. military official said. Kiowas usually have a crew of two pilots. U.S. military officials do not believe the helicopter was hit by hostile fire, Lt. Col. James Hutton said.

The crash came two days after a CH53E Super Stallion (search) helicopter transporting troops went down in bad weather in the western desert, killing 30 Marines and one sailor — in the deadliest single incident for U.S. forces in Iraq since the March 2003 invasion. The military is still investigating the cause of that crash.

The arrested al-Zarqawi associates included Salah Suleiman al-Loheibi (search), the head of his group's Baghdad operation, who met with al-Zarqawi more than 40 times over three months, said Qassim Dawoud, a top security adviser to Iraqi Prime Minister Ayad Allawi.

Dawoud said Ali Hamad Yassin al-Issawi (search), another associate, was also captured. Dawoud said the two arrests took place in mid-January but gave few details.

Also captured was al-Zarqawi's military adviser, a 31-year-old Iraqi named Anad Mohammed Qais, 31, said Deputy Prime Minister Barham Saleh.

Asked by reporters if authorities were close to arresting al-Zarqawi himself, Saleh replied: "We are getting close to finishing off al-Zarqawi and we will get rid of him."

The Jordanian-born Al-Zarqawi heads Al Qaeda's affiliate in Iraq, which like other militant groups has threatened to kill anyone who takes part in Sunday's election. It repeated those warnings in a new Web message Friday, telling Iraqis they could get hit by shelling or other attacks if they approach polling stations, which it called "the centers of atheism and of vice."

"We have warned you, so don't blame us. You have only yourselves to blame," it said.

On Thursday, the group posted a video on the Internet showing the murder of a candidate from Allawi's party. The tape included a warning to Allawi personally: "You traitor, wait for the angel of death."

Friday's announcement brings to six the number of purported al-Zarqawi lieutenants arrested recently — including a deputy who allegedly mastermined car bomings, a propoganda chief and a weapons supplier, whose arrests were announced earlier this month.

The announcement appeared aimed at bolstering public confidence in security forces in advance of Sunday's election. Officials fear a low turnout — particularly among Sunni Arabs — could tarnish the legitimacy of the new government. Iraqis will choose a 275-member National Assembly and governing councils in the country's 18 provinces.

The U.S. ambassador in Baghdad, John Negroponte, 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's "The Early Show." "I think you're going to see participation across the board."

Iraq's Shiite Muslim majority is eager to vote, expecting the election to establish their domination of the country after decades of repression. Sunni Arabs, however, may follow calls by some leaders to boycott the vote — or may be intimidated by the violence that has been at its worst in mainly Sunni regions north and west of Baghdad.

Expatriate Iraqis began casting ballots amid tight security in early voting in 14 countries from Australia to Sweden to the United States.

"This is a long dream that now comes true," said 56-year-old Karim Jari before casting his vote in Sydney, Australia, where young children mingled in line with elderly Kurdish women in head-to-toe black robes and men in colorful traditional costumes. "We hope this is a new beginning."

Five U.S. soldiers were killed in Baghdad on Friday — three of them in a single roadside bomb that hit a patrol in a western district. The other two were killed in a bomb in southern Baghdad and a shooting across town.

The two American soldiers from Task Force Baghdad were killed Friday in two separate incidents in Baghdad, one when a roadside bomb went off, the other in a shooting on the other side of the capital about 15 minutes later, the military said.

More than 1,414 U.S. troops have been killed in Iraq since fighting began in March 2003.

Friday's homicide car bombing rattled Baghdad's Doura neighborhood, a flashpoint in recent days, with several street battles between insurgents and Iraqi National Guard troops and 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, damaging 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.

President Bush, in an interview published in The New York Times on Friday, said he would withdraw the 150,000 U.S. forces from Iraq if the new government formed after Sunday's vote asks for a pullout. But Bush said he expected the country's new leaders would want multinational forces to stay.

"I've, you know, heard the voices of the people that presumably will be in a position of responsibility after these elections — although you never know," Bush said in an interview with the newspaper. "But it seems like most of the leadership there understands that there will be a need for coalition troops at least until Iraqis are able to fight."