BAGHDAD, Iraq — A commercial helicopter was shot down by missile fire north of the Iraqi capital Thursday, killing 11 people, including six American contractors, officials said.

Bulgaria's Defense Ministry said the helicopter was downed by missile fire and the victims included a three-member Bulgarian crew.

A Toronto-based charter company said there were two bodyguards from Fiji on board, while Bulgaria's Transport Ministry said they were from the Philippines.

The Philippine mission in Baghdad said it had no information that any of its nationals were on the helicopter.

The six Americans worked for security contractor Blackwater USA, the U.S. Embassy said. The North Carolina-based contracting firm provides security for State Department officials in Iraq.

Two U.S. military officials in Baghdad initially said the helicopter was contracted by the Defense Department, but the U.S. Embassy later said that was untrue. It gave no information on the contractor.

It was unclear whether the civilian employees of Blackwater were under contract to the Pentagon or the State Department, U.S. officials in Washington said.

Last year, four Blackwater employees were killed in Fallujah, and their bodies were burned and mutilated. Two of the corpses were strung up on a bridge over the Euphrates River.

The deaths touched off a Marine assault on insurgents in the city.

The Mi-8 helicopter went down about 12 miles north of Baghdad, the U.S. Embassy said. Video on television showed burning wreckage from the Russian-built craft and personal belongings scattered across a wide area.

The helicopter was owned by Bulgaria-based Heli Air and chartered by Toronto-based SkyLink Aviation Inc., said SkyLink air operations manager Paul Greenaway. The helicopter was flying to Tikrit, he said.

Greenaway said the six Americans were "doing some sort of security work." He said the victims included three Bulgarian crew members and two security guards from Fiji.

On March 13, two American security contractors working for Blackwater Security — a subsidiary of Blackwater USA — were killed and a third was wounded in a roadside bombing south of Baghdad on the main road to Hillah.

Elsewhere Thursday, relatives of Iraqis who have disappeared in a Sunni militant stronghold known as the "Triangle of Death" gathered at a police station in Suwayra to examine photographs of the bodies of dozens of Iraqis that officials said were pulled from the Tigris River in recent weeks.

"My cousin was kidnapped by terrorists, and he has been missing for two weeks," Jawad Hashim Shael said as he scanned the photos. "We have searched all nearby areas, but we still have no information about his whereabouts."

On Wednesday, interim President Jalal Talabani announced that more than 50 bodies were recovered, saying that was proof of claims that dozens were abducted from an area south of the capital last week despite a fruitless search by Iraqi forces.

Talabani did not say when or where the bodies were pulled from the river, but he said all had been identified as hostages.

"Terrorists committed crimes there. It is not true to say there were no hostages. There were. They were killed, and they threw the bodies into the Tigris," Talabani said. "We have the full names of those who were killed and those criminals who committed these crimes."

Shiite leaders and government officials claimed last week that Sunni militants abducted as many as 100 Shiites from the Madain area, 14 miles southeast of Baghdad, and said they would be killed unless all Shiites left town.

But when Iraqi forces moved into the town of 1,000 families, they found no captives, and residents said they had seen no evidence anyone had been seized.

Madain and Suwayra are both located in the "Triangle of Death," a region south of Baghdad where there have been numerous retaliatory kidnappings. Police and health officials said victims were sometimes killed and dumped in the river.

As summer approaches and temperatures start to rise, bodies have been floating to the surface, said Dr. Falah al-Permani of the Swera district health department. He said as many as 50 bodies have been recovered in the past three weeks. But it was unclear whether they were the bodies referred to by Talabani.

After a week of stepped-up violence, the country's most feared terror group, Al-Qaida in Iraq, claimed responsibility Thursday for a suicide car bombing that targeted interim Prime Minister Ayad Allawi's convoy but did not harm the Iraqi leader.

The attack on Allawi's convoy occurred Wednesday, a day of multiple bombings and shootings in Baghdad and elsewhere that killed at least 13 people and wounded 21.

The victims included an Australian security contract worker and two other foreign nationals killed by assailants firing at their vehicle in Baghdad, Australian officials said in Sydney on Thursday.

Al-Qaida in Iraq claimed responsibility for several of the attacks, including the one on Allawi, in statements that surfaced on Web sites known for their militant content.

"Allawi escaped, but if one arrow missed its target, there are many others in the quiver," one of the statements said.

The authenticity of the claims could not be verified.

In a separate attack, a roadside bomb exploded on the highway leading to Baghdad's airport Thursday, heavily damaging three sport utility vehicles carrying civilians. Police Capt. Hamid Ali said two foreigners were killed and three wounded in the burning vehicles. But U.S. Embassy and military officials could not confirm the casualties.

Lately, much of Iraq's violence has occurred in the capital, as political leaders struggle to agree on a new Cabinet from the country's mix of Sunnis, Shiites and Kurds, nearly three months after Iraqis elected a 275-seat National Assembly.

Meanwhile, the Iraqi Defense Ministry identified 19 bullet-riddled bodies found Wednesday in Haditha, 140 miles northwest of Baghdad, as fishermen. Residents initially said they believed the victims were soldiers.

Investigations indicated the men came from the southern Diwaniya and Najaf provinces to fish in Tharthar lake when they were captured by insurgents, taken to the soccer stadium at nearby Haditha and shot, said chief ministry spokesman Saleh Sarhan. He did not say how the victims had been identified or why they might have been captured.

Residents heard gunshots Wednesday and rushed to the stadium, where they said they found the bodies.

AP military writer Robert Burns in Washington and reporters Veselin Toshkov in Sofia, Bulgaria, and Beth Duff-Brown in Toronto contributed to this report.