BAGHDAD, Iraq -- American troops backed by helicopters and war planes launched a major offensive against followers of Iraq´s most wanted insurgent, Abu Musab al-Zarqawi, in a desert area near the Syrian border, and as many as 100 militants were killed, U.S. officials said Monday.

Marines, sailors and soldiers from Regimental Combat Team 2, 2nd Marine Division, were conducting the offensive in an area north of the Euphrates River, in the al-Jazirah Desert, a known smuggling route and sanctuary for foreign insurgents, the U.S. military said.

The brief statement did not specify when the operation began, how many troops were involved, or whether there had been any American casualties. But U.S. military spokesmen later said the offensive started on Saturday and that it had killed as many as 100 militants. The military also reported that two U.S. Marines were killed in the area on Sunday and one on Monday.

A senior U.S. military official said the operation is targeting a group of al-Zarqawi followers believed to be operating in the area. He spoke on condition of anonymity.

Al-Zarqawi, a Jordanian, is leader of the terrorist group al-Qaida in Iraq. He has declared allegiance to Osama bin Laden´s al-Qaida network and is tied to many bombings and kidnappings since the U.S.- led invasion removed Saddam Hussein from power two years ago.

Meanwhile, militants claimed in a Web posting they took a Japanese man hostage after ambushing a group of foreigners and Iraqi troops in western Iraq.

The Ansar al-Sunnah Army identified the Japanese hostage as Akihito Saito, 44, and posted a photocopy of his passport, including his picture, on the group´s Web site.

The group said Saito was seized after Ansar al-Sunnah fighters ambushed a convoy of five foreign contractors, protected by 12 members of the Iraqi security forces. It claimed all were killed in the fight except for Saito, who was "severely injured."

One of the posted ID cards belonging to Saito identified him as a security manager of Hart GMSSCO, a British-based security firm. Hart CEO Simon Falkner said in London that there was an ambush with casualties Sunday night involving Hart personnel, but would not confirm whether Saito was an employee and if he had been seized.

The group claimed it ambushed the convoy near Hit, west of Baghdad, and said a fierce battle erupted between the fighters and those in the convoy. Hit is about 80 miles from where U.S. forces have launched a major offensive against militants near the Syrian border. It was not known if the offensive had any connection to the ambush.

Six bodies also were found Monday in Markab al-Tair village, near the Syrian frontier, police Col. Wathiq Mohammed said. He identified them as a senior Iraqi border policeman and five of his relatives.

The offensive is one of the largest involving U.S. troops since American and Iraqi forces took over the insurgent bastion of Fallujah in November. Two weeks ago, about 1,000 U.S. soldiers completed a four-day operation against insurgents north of Baghdad where a civilian helicopter was shot down.

The military has stepped up raids on suspected hideouts across the country, including near the Syrian border, where U.S. and Iraqi officials say foreign militants are entering the country to attack coalition forces.

The Chicago Tribune reported that more than 1,000 U.S. troops supported by fighter jets and helicopter gunships raided villages Sunday in and around Obeidi, about 185 miles west of Baghdad, in an operation expected to last several days.

The report, by a journalist embedded with the U.S. forces, said the offensive "was seeking to uproot a persistent insurgency in an area that American intelligence indicated has become a haven for foreign fighters flowing in from Syria."

Some U.S. forces were able to conduct limited raids north of the Euphrates and predator drones provided surveillance Sunday, but most troops were stuck south of the waterway as engineers tried to build a pontoon bridge there, the Tribune said.

It also quoted some Marines as saying residents of one riverside town turned off all their lights at night, apparently to warn neighboring towns of the approaching U.S. troops.

"Our analysis is that there´s a foreign fighter flow from Syria," Col. Stephen Davis, commander of Marine Regimental Combat Team 2, told the Tribune. "The trademark of these folks is to be where we´re not. We haven´t got north of the river for a while."

On Sunday, the U.S. military said coalition forces killed six insurgents and detained 54 suspects in raids targeting al-Qaida in Iraq, in Qaim, a Syrian border town about 200 miles west of Baghdad. Coalition forces said they acted on information received from Mohammed Amin Husayn al-Rawi, an al-Zarqawi associate captured April 26.

The crackdown came amid insurgent violence that has killed more than 310 people since April 28, when a new Iraqi government was announced with seven positions left undecided. At least nine American servicemen were killed over the weekend.

Iraq´s interim National Assembly on Sunday approved six more Cabinet members, including four more Sunni Arabs. But the Sunni man selected as human rights minister turned down the job because he didn´t want to be chosen on a sectarian basis, tarnishing the Shiite premier´s bid to include the disaffected minority believed to be driving the insurgency.

The five new members were sworn in Monday. The rest of Cabinet also repeated the oath of office after new language was added at the request of Barham Salih, the Kurdish planning and development cooperation minister. The ministers pledged their allegiance to a "federal, democratic" Iraq, which Salih said brought the wording of the oath in line with language in Iraq´s transitional law.

Iraq´s two main Kurdish factions, which hold 75 seats in the 270- member National Assembly, are pressing for a federal government that would give strong autonomy to the Kurdish north.

When complete, the new government is expected to include 17 Shiite ministers, eight Kurds, six Sunnis and a Christian. Three deputy premiers have been named _ one each for the Shiites, Sunnis and Kurds, with the fourth held open for a woman.

Prime Minister Ibrahim al-Jaafari pledged Sunday to take "all necessary measures" to restore security in Iraq and said the government could impose martial law to fight the insurgents.

Violence continued Monday with three Iraqis killed in a suicide car bombing at police checkpoint at a busy Baghdad intersection, said police Maj. Mousa Abdul Karim. The dead included two policemen and a civilian. Six other policemen and three civilians were wounded, he said.

At least three other car bombs exploded in Baghdad later Monday, including one that wounded an unidentified number of Iraqi soldiers at a checkpoint, said U.S. military spokesman Master Sgt. Greg Kaufman.

The U.S. military said it had conducted several raids Sunday in and around Baghdad, detaining 13 suspected insurgents, some armed with rocket-propelled grenades.

Two of the suspects were captured in a raid aimed at the leader of a terror cell believed to have plotted an April 20 assassination attempt against former Prime Minister Ayad Allawi, the military said. Allawi was unhurt, but at least one policeman was killed and two wounded by a suicide car bomb.

On Sunday, the Iraqi government said its security forces had captured another al-Zarqawi associate. He was identified as Ammar Adnan Mohammed Hamza al-Zubaydi, also known as Abul Abbas. Al- Zubaydi is accused of planning an April 2 assault by dozens of insurgents who blew up car bombs and fired RPGs outside Abu Ghraib prison, the Iraqi statement said.

At least 1,603 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count. (Copyright 2005 Associated Press. 05/09/05)