The U.S. military bombed the sparsely populated southern edge of Baghdad (search) overnight to root out insurgents believed to be launching mortar shells and rockets, hours after a U.S. military helicopter was shot down west of the capital, killing one soldier.

Soon after the helicopter crashed on Friday, the military said attackers posing as journalists fired assault weapons and rocket-propelled grenades at American paratroopers guarding the burning aircraft.

But there was confusion since Reuters news agency reported that its team at the scene was fired at by U.S. troops and three were later detained by the military.

Elsewhere, insurgents attacked an American tanker convoy, setting one ablaze, and coalition forces raiding a Sunni Muslim (search) mosque arrested 32 suspected non-Iraqi Arab insurgents and seized an arms cache. Hundreds of Iraqis protested outside the mosque after the raid.

In Baghdad, a military spokesman said the shelling of the Doura neighborhood was part of Operation Iron Grip (search). Residents said it appeared U.S. fire was targeting fields in the neighborhood.

Bordered by date palm farms, the sparsely populated area once was home to a number of former officials in Saddam Hussein's government and is now the site of a U.S. military base.

Operations like Iron Grip send "a very clear message to anybody who thinks that they can run around Baghdad without worrying about the consequences of firing (rocket propelled grenades), firing mortars," U.S. Army Brig. Gen. Mark Kimmitt told reporters Friday. "There is a capability in the air that can quickly respond against anybody who would want to harm Iraqi citizens or coalition forces."

He said troops from the 82nd Airborne Division were "fairly convinced that it was enemy fire" that brought down the OH-58 Kiowa Warrior helicopter near Fallujah, a flashpoint in the insurgency.

As paratroopers from the 82nd surrounded the crash site, five men "wearing black press jackets with 'press' clearly written in English" fired on them, Kimmitt said. He said it was the first time he had heard of assailants in Iraq posing as journalists.

The Reuters team was led by Iraqi cameraman Salem Uraiby, who was filming from a checkpoint using a camera on a tripod and was wearing a flak jacket clearly marked "press," the agency said

"We were fired on and we drove away at high speed," driver Alaa Noury said. He said a second car driven by another Iraqi journalist had been fired upon in the same incident. One of the cars remained in Fallujah, Reuters said.

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

Rebels previously have shot down U.S. helicopters elsewhere in the so-called "Sunni Triangle," the heartland of Saddam's 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 on Nov. 15 when two Black Hawk helicopters collided above Mosul in what the military called a likely grenade attack.

Also Friday, hundreds of angry protesters gathered outside the Ibn Taymiyyah mosque after U.S. soldiers and Iraqi defense force officers raided the mosque overnight.

Kimmitt said the U.S and Iraqi soldiers 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.

A 5,000-gallon oil tanker also erupted in flames near a U.S. military base on the road to the western town of Ramadi. 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 on 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 Iraqi officials, U.S. soldiers captured Abu Mohammed, believed to be moving foreign fighters and cash through a tense area west of Baghdad, and three other suspects, the military said Friday.

Soldiers in Samarra 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.