Jordanian militant Abu Musab al-Zarqawi (search)'s group has claimed responsibility for an attack on U.S. forces in western Baghdad earlier this week, according to a statement posted on an Islamic Web site Wednesday.

The military wing of al-Zarqawi's Tawhid and Jihad group claimed 100 of its fighters attacked U.S. forces on Monday in al-Saqlawiya (search), 43 miles west of the Iraqi capital.

The statement did not specify how many American soldiers were injured or killed.

The U.S. military on Tuesday announced that three Marines assigned to the 1st Marine Expeditionary Force were killed while on duty in western Iraq. Two died in action Monday in the Anbar province, while a third died of his wounds later Monday.

Another four U.S. Marines were killed Tuesday in the Anbar province while conducting security and stability operations on Tuesday, the U.S. military said in a statement Wednesday.

The area is a volatile Sunni Muslim-dominated region of Iraq extending from the outskirts of Baghdad to the borders of Syria and Jordan.

"One hundred of the lions of God ... made a trap in al-Saqlawiya for the American devil soldiers," the statement claimed. It also said that two helicopters and two humvees, including the U.S. forces inside the vehicles, "were destroyed."

The United States is offering $25 million for information leading the capture of al-Zarqawi, who is believed to be behind a series of coordinated attacks on police and security forces that killed 100 people only days before U.S. forces handed over power to an Iraqi interim government.

His followers have also claimed responsibility for the beheading of American Nicholas Berg (search) and South Korean Kim Sun-il (search).

An armed vigilante group, calling itself "Salvation Movement," threatened on Tuesday to kill al-Zarqawi for insurgency attacks that have killed Iraqis, making the first internal threat against the Jordanian militant.