BAGHDAD, Iraq (AP) _ Two U.S. soldiers guarding a gas station were wounded in a drive-by shooting in the northern city of Mosul on Wednesday, and American troops in another northern city arrested five Iraqi policemen and 24 others suspected of ties to insurgents.

Also Wednesday, the U.S. military said the emergency landing of a U.S. helicopter near Fallujah, west of Baghdad, was likely the result of ground fire by insurgents.

In the Mosul attack, U.S. soldiers returned fire and killed one assailant, a spokesman for the U.S. Army's 101st Airborne Division said on condition of anonymity.

But witnesses said the attackers escaped and U.S. troops opened fire on passing cars, killing a driver in the line of fire. Witnesses identified the man as a member of the Patriotic Union of Kurdistan, or PUK, a major pro-American political party. The PUK's Mosul headquarters is across the street from the gas station.

An Associated Press reporter saw blood stains at the spot where witnesses said the soldiers had stood, and a bullet-riddled and bloodstained car said to belong to the PUK member.

Early Wednesday, U.S. troops and Iraqi police in the oil-rich northern city of Kirkuk arrested 29 people, including five policemen, who were suspected of ties to the former regime of Saddam Hussein, said Adnan Mohammed Saleh, a city police officer. Saleh said the policemen were suspected of passing intelligence to anti-occupation rebels.

In the downing of the helicopter, the U.S. military said the OH-58D Kiowa observation helicopter took fire Tuesday just south of the town of Fallujah, west of Baghdad, and was forced to make an emergency landing.

A U.S. military official who declined to be identified said Wednesday that a preliminary examination indicated the aircraft had been brought down by small-arms fire or a projectile fired from the ground. Neither of the two crew members was injured.

It was the fifth U.S. helicopter downed in Iraq in just over five weeks.

Fallujah has been a focus of resistance to the U.S. occupation, although the city has been relatively peaceful of late. The town sits in the heart of the Sunni Triangle where the majority of attacks on American forces have occurred since the ouster of Saddam.

In Baghdad on Wednesday, 3,000 funeral marchers mourned three men killed in a bombing of a Sunni mosque a day earlier. The mosque's imam, Farouk Khamis, accused Shiite Muslim extremists of carrying out the attack.

``Prominent Shiite clerics are urged to deter those politically motivated groups so that the unity of Muslims in this country can be preserved,'' Khamis told the mourners.

Also Wednesday, Iraq-based members of the Iranian opposition group, the Mujahedeen Khalq, denounced a decision by Iraq's U.S.-appointed Governing Council to expel them from the country by the end of the year.

In a statement released at the group's camp northeast of Baghdad, the group said the decision favored Iran's efforts to establish a ``satellite theocratic dictatorship in Iraq.''

Mujahedeen members should be out of Iraq by the end of the year and the group's offices in Iraq will be closed, the Governing Council said. A reporter who visited the group's Baghdad office on Wednesday found it occupied by squatters who said the militia had abandoned it.

The group has battled Iran's theocratic regime since the late 1970s. In 1999, it was listed as a terrorist organization by the U.S. State Department.

Over the years, the U.S. government had maintained an ambiguous posture toward the group, even allowing it and an associated organization, the Paris-based National Council of Resistance of Iran, to maintain offices in Washington. In August, however, the State Department shut down both groups' offices, earning rare praise from Iran.

In Baghdad, Iraq's interim government voted to establish a war crimes tribunal to prosecute top members of Saddam's regime, two people who attended the meeting said. Officials planned to establish the tribunal Wednesday.

U.S. authorities are holding several dozen of Saddam's top aides who could be tried under the new measure.