Enemy fighters shot down a U.S. military helicopter west of Baghdad on Friday, killing one soldier, and attackers posing as journalists fired assault weapons and rocket-propelled grenades at American paratroopers guarding the burning aircraft, the military said.

Elsewhere, Arab gunmen shot and killed a Kurd amid rising ethnic tensions in the northern, oil-rich city of Kirkuk, and a minor Baath party official was assassinated in an apparent revenge killing. An American tanker was set ablaze in a rebel attack, and coalition forces raiding a Sunni Muslim mosque arrested 32 suspected non-Iraqi Arab insurgents and seized an arms cache.

In Baghdad, U.S. Army Brig. Gen. Mark Kimmitt said enemy fire likely brought down the OH-58 Kiowa Warrior that crashed near Fallujah, a flashpoint in the insurgency.

Troops of the 82nd Airborne Division "are fairly convinced that it was enemy fire," Kimmitt said.

Soon after, five men "wearing black press jackets with 'press' clearly written in English" fired on U.S. paratroopers guarding the crash site, Kimmitt said. He said it was the first time he had heard of assailants in Iraq posing as journalists.

The attackers fled in two cars. Soldiers doing a sweep through the town, with helicopters circling overhead, tracked down one of the cars and arrested four "enemy personnel," Kimmitt said.

Rebels have previously shot at and brought down U.S. helicopters elsewhere in the so-called "Sunni Triangle (search)," the heartland of Saddam Hussein's (search) support and a center of resistance to the U.S.-led occupation.

In the deadliest single attack on U.S. forces since the Iraq invasion began in March, 17 soldiers were killed when two Black Hawk helicopters collided above Mosul in what the military called a likely grenade attack.

In Baghdad, people protested outside the Ibn Taymiyyah mosque Friday after U.S. soldiers and Iraqi defense force officers raided the mosque overnight.

Kimmitt said they seized explosives, guns and ammunition and arrested 32 people believed to be non-Iraqi Arabs "based on their dialect." The military says foreign Islamic militants opposed to the occupation have infiltrated from neighboring borders.

In the northern city of Mosul, a minor Baath Party official and Saddam-appointed dean of political science of Mosul University, Adel Jabar Abid Mustafa, was found Thursday with two gunshots to his head, according to the dean's brother, Salim Abid Mustafa.

Gunmen in Mosul have killed at least three judges appointed by Saddam's regime, as well as officers in a new Iraqi police force formed by the U.S.-led occupation.

Also Friday, a truck traveling toward Baghdad International Airport flipped on its side, killing one soldier and injuring six others, the military said.

An 5,000-gallon oil tanker erupted in flames near a U.S. military base on the road to the western town of Ramadi on Friday. The military said it was in a convoy attacked with a roadside bomb, a grenade and small arms fire. Three American soldiers suffered burns and shrapnel wounds.

U.S. military commanders say rebel attacks on troops have decreased since Saddam's capture Dec. 13, but that insurgents may be shifting to softer, civilian targets. On New Year's Eve, a car bomb destroyed an upscale Baghdad restaurant, killing eight people.

In ongoing raids to hunt down former Saddam officials, U.S. soldiers captured Abu Mohammed, believed to be moving foreign fighters and cash through a tense area west of Baghdad, the military said Friday. Based on information gleaned from the arrest Thursday, the military seized another three suspects and some weapons.

U.S. soldiers also arrested tribal leader Sheik Kahtan Yehia of the Albu Rahman tribe in Thursday night raids in Samarra, northwest of Baghdad, witnesses said. They said soldiers accused the sheik of sheltering the most-wanted man in Iraq since Saddam's capture, former Vice President Izzat Ibrahim al-Douri.

Soldiers in Samarra also blew up the house of Talab Saleh, who is accused of orchestrating attacks against U.S. troops, witnesses said. They said the troops arrested Saleh's wife and brother and said they would not be released until Saleh surrenders. The military had no immediate comment.

Norwegian police, meanwhile, arrested the spiritual leader of Ansar al-Islam (search), an Islamic militant group based in northern Iraq that is regarded as a terrorist organization by the United States and the United Nations.

Mullah Krekar was arrested Friday at his house in Oslo on charges of plotting to assassinate his rivals in northern Iraq three years ago, his lawyer said.

American soldiers killed three suspected Ansar al-Islam members in a firefight in the northern city of Mosul last week that left two soldiers wounded.

In Kirkuk, Arab gunmen killed one Kurd and wounded another on Thursday night as they were walking in an Arab neighborhood, Police Chief Gen. Turhan Youssef said.

Afterward, there was a shootout between Arabs and police, who killed two attackers and wounded several, said Jalal Jawher, local head of the Patriotic Union of Kurdistan party.

Tensions in Kirkuk have been high since an attack Wednesday on Arab and Turkmen protesters demanding that Kirkuk remain under the administration of a central Iraqi government.

The city's 1 million-plus residents are divided in roughly equal parts among three ethnic groups -- Arab, Turkmen and Kurd.

Some Kurds have been calling for Kirkuk to join autonomous Kurdistan, a Switzerland-sized area of northern Iraq where Kurds have ruled themselves since the end of the 1991 Gulf War under U.S.-led aerial protection.