Gunmen carrying flags of Iraq's most feared terror group surfaced in force in the central Iraqi city of Samarra on Tuesday for the first time since U.S. troops briefly entered it in a deal with tribal leaders that the Americans had portrayed as a success story in battling the insurgency.

Dozens of masked gunmen carrying automatic rifles and rocket-propelled grenades drove through the main streets of Samarra, 60 miles north of Baghdad, in about 20 vehicles.

Some carried the black flags of Iraq's most-feared terror organization, Tawhid and Jihad (search), which is run by Jordanian-born Abu Musab al-Zarqawi (search).

The group has claimed responsibility for the brutal slayings of foreign hostages, including two American civil engineers and an American businessman.

Two of the cars carrying the gunmen were police pickup trucks that appear to have been confiscated by the insurgents. The gunmen stopped some cars and asked passengers to hand over music tapes, giving them tapes with recitations from the Muslim holy book, the Quran, in exchange.

After a two-hour drive-through, the convoy dispersed around noon and the gunmen could not be seen in the streets. It was not clear why they left.

Samarra has been under insurgent control and a virtual "no-go" area for U.S. troops since May 30.

The Americans returned briefly on Sept. 9 under a peace deal brokered by tribal leaders by which U.S. forces agreed to provide millions of dollars in reconstruction funds in exchange for an end to attacks on American and Iraqi troops.

U.S. and Iraqi commanders portrayed the deal as a success story in their attempts to put down the 17-month-old insurgency that aims to drive foreign forces from the country.

In recent weeks, however, the city witnessed sporadic clashes between U.S. troops and insurgents.

A suicide attacker detonated a car bomb on Sept. 19, near a U.S.-Iraqi checkpoint in the city, killing three people and wounding seven, including four U.S. soldiers. More deadly clashes broke out there Sept. 22.

American military commanders have indicated that Samarra, along with Fallujah and the Baghdad slum known as Sadr City (search) may have to be subdued prior to a general election in January.