A car bomb ripped through a crowded mosque during Friday prayers, killing eight people and wounding 26 in the latest attack targeting Iraq's Shiite majority. One section of the mosque collapsed, frantic worshippers searched through rubble for loved ones, and women wailed and beat their chests in grief.

The U.S. military (search), meanwhile, sent investigators to the site where a helicopter carrying 11 civilians was shot down Thursday. A video posted on a militant web site suggested a crew member may have survived the crash, only to be gunned down by insurgents. The Bulgarian company that owns the helicopter confirmed Friday the man seen in the footage was one of the aircraft's pilots.

The violence was part of a surge of dramatic attacks that have caused heavy casualties in recent weeks, ending a relative lull since Iraqis voted in historic Jan. 30 elections. Iraqi leaders are struggling to form a Cabinet that will include members of the Sunni minority, believed to be the driving force in the insurgency.

One U.S. soldier was killed Friday by a roadside bomb north of Tal Afar (search), 93 miles east of the Syrian border, the military said. On Thursday, a U.S. Marine died in a non-hostile incident at Camp Delta, near Karmah, 50 miles west of Baghdad, the military said. It gave no details.

Al-Jazeera (search) aired part of a video Friday in which it said a militant group was threatening to kill three kidnapped Romanian journalists and their Iraqi American translator unless Romanian troops leave Iraq within four days.

The car bomb exploded at Al-Subeih mosque, in the capital's Shiite dominated eastern New Baghdad neighborhood, said police Col. Ahmed Aboud. Witnesses said the vehicle used in the attack had been parked outside the building since the morning.

Officials at al-Kindi Hospital (search) said a 10-year-old child was among the eight dead, and the 26 wounded included two 9-year-olds.

Body parts were strewn at the scene amid piles of bricks, shattered glass and pools of blood. One man clutched a child's foot, shaking and weeping.

"This is a cowardly and savage act that aims to create conflict among Iraqis," said Abdelallah Faraj, a grocery store owner who survived the attack.

Shiite mosques and funerals have become a frequent target of Sunni-led insurgents. In February, suicide bombers attacked a number of them during the Shiite commemoration of Ashoura, killing nearly 100 people. In recent weeks, police have been pulling dozens of bodies from the Tigris River in a region south of Baghdad that has seen numerous retaliatory kidnappings and killings by Shiite and Sunni groups.

North of the capital, Col. Paul Bricker lead a team of investigators who surveyed the site where the helicopter crashed Thursday, the military said.

The chartered flight between Baghdad and Tikrit was believed to be the first civilian aircraft shot down in Iraq since the U.S.-led invasion two years ago. A spokesman for U.S. forces in Iraq said an American medevac team arrived at the site within half an hour of Thursday's crash and found no survivors.

The dead included six American bodyguards for U.S. diplomats, three Bulgarian crew and two security guards from Fiji, officials said.

The remains of those killed were taken to Balad Air Base (search), and an aircraft recovery team from the 3rd Infantry Division was moving the wreckage to Baghdad International Airport for further inspection, the military said.

Two militants groups claimed responsibility for shooting down the Russian-made Mi-8 helicopter and released video to support their claims.

A group calling itself the Islamic Army in Iraq posted a footage on the Internet purporting to show militants capturing and shooting the lone survivor, found lying in the grass amid burning wreckage and charred bodies.

Mihail Mihailov, the manager of Heli Air, the Bulgarian company that owned the helicopter, identified the man in the footage as Lyubomir Kostov, one of the aircraft's two pilots.

Al-Jazeera broadcast another video from a group calling itself the Mujahedeen Army in Iraq that showed the helicopter flying about 100 feet above the ground. The camera suddenly shakes, swinging down to show the ground near the cameraman's feet — apparently as a missile hits the helicopter.

When the camera turns again toward the sky, the helicopter is in flames, arcing toward the ground with a pall of black smoke trailing behind it.

There was no independent confirmation of the authenticity of either video.

Toronto-based SkyLink Aviation Inc. chartered the helicopter, and the six Americans on board were employed by Blackwater Security Consulting, a subsidiary of North Carolina-based security contractor Blackwater USA.

Both companies were invited to participate in the investigation, the military said. But Blackwater said it would not be involved as the helicopter did not belong to the company and wasn't being flown by its employees.

The Bulgarian government and Heli Air said they were sending investigators.

The hostage video showed the three Romanians — two men and a woman — sitting cross-legged against a wall with their hands chained. A man said to be their translator is shown sitting alone, hands bound. Gunmen stand on either side of him, pointing an automatic rifle and a pistol at his head.

Journalists Marie Jeanne Ion, Sorin Dumitru Miscoci and Ovidiu Ohanesian were kidnapped with their translator, Mohammed Monaf, on March 28 near their Baghdad hotel shortly after interviewing interim Iraqi Prime Minister Ayad Allawi. They appeared a day later in a video aired on Al-Jazeera.

In the footage aired Friday, a woman said to be Ion is seen talking but Al-Jazeera did not air the audio.

In Bucharest, colleagues of two of the captives from the Romanian Prima TV station held a protest late Friday in front of the Cotroceni presidential palace to demand their release.

More than 200 foreigners have been kidnapped in Iraq since the beginning of 2004, and at least 17 are believed to still be in the hands of their captors. More than 30 others were killed by their kidnappers.

In other violence Friday:

— Two roadside bombs exploded in Baqouba, northeast of Baghdad, killing a 7-year-old girl and wounding a man, police said.

— Insurgents attacked an Iraqi army checkpoint in nearby Muradiyah with mortars and small arms fire, injuring five Iraqi soldiers, police said.

— A high-ranking police officer was killed and his wife and daughter injured in a drive-by shooting in the northern city of Mosul, police said.