Insurgents brought down a Russian-made helicopter carrying 11 civilians with missile fire north of the capital Thursday and said they captured and shot to death the lone crew member who survived. The dead from the crash included six American bodyguards for U.S. diplomats.

The chartered flight was believed to be the first civilian aircraft shot down in Iraq since the U.S.-led invasion two years ago.

An Internet statement by a group identifying itself as the Islamic Army in Iraq (search) was accompanied by a video showing the repeated shooting of a man who was found in tall grass and forced to stand up and walk. The video showed burning wreckage just before the shooting.

"One of the crew members was captured and killed," the statement said.

The man who was shot to death in a grassy field spoke English with an accent and was wearing a blue flight suit, indicating he was one of the three Bulgarian crew members. Two Fijian helicopter security guards were also on board the flight.

The video also showed two charred bodies near the burning wreckage, about 12 miles north of Baghdad.

The authenticity of the video, posted on a Web forum often used by militant groups, could not be confirmed. A U.S. Embassy official in Baghdad said he had no knowledge that anyone on board survived the crash and was killed later.

The Mi-8 helicopter (search) was shot out of the air as growing numbers of contractors, diplomats and other civilian officials are turning to aircraft to avoid insurgent attacks on Iraq's roads.

The downing is part of a surge of attacks that have caused heavy casualties in recent weeks, ending a relative calm since January elections. In the latest violence, two U.S. Marines and at least five other people, including two foreign civilians, were killed in attacks Wednesday and Thursday.

The six Americans on board the downed helicopter were employed by Blackwater Security Consulting — a subsidiary of North Carolina-based security contractor Blackwater USA, which had four employees slain and mutilated by insurgents in Fallujah a year ago.

The Americans were assisting the Bureau of Diplomatic Security (search) in protecting U.S. diplomats in Iraq.

"They played a critical role in our effort to bring a better way of life to the people of a country who have not experienced freedom and opportunity for many years," State Department spokesman Adam Ereli said.

Blackwater said another of its guards was killed and four were wounded Thursday when an explosive device was detonated next to one of its armored personnel carrier near Ramadi.

The Islamic Army statement said it killed the survivor "in revenge for the Muslims who have been killed in cold blood in the mosques of tireless Fallujah before the eyes of the world and on television screens, without anyone condemning them." It was apparently referring to the shooting by an American soldier of a wounded Iraqi in a Fallujah mosque on Nov. 13 during a U.S. offensive in the city.

In the video, militants come across the injured man in the flight suit. "Stand up! Stand up!" an insurgent orders the man, who reaches out and says "Give me a hand."

Then, apparently referring to a fractured leg, he says "It's broken."

The militants — unseen except in brief glances — tell him to stand up. "Weapons? Weapons?" the gunmen ask him in Arabic as he stands uneasily.

They tell him, "Go!", and he starts to hobble away with his back to the camera. Then there are voices and he turns to the side, holding up a hand. Then the shooting begins, bullets hitting his body as he falls backward into the grass. The insurgents can be heard shouting "Allahu akbar," or "God is great," as he goes down. More bursts of gunfire then hit the body.

Ereli, who spoke before the video was posted, said he could not confirm the cause of the crash.

However, the Bulgarian Defense Ministry said the helicopter was struck by missile fire.

The aircraft was owned by Heli Air of Bulgaria and chartered by Toronto-based SkyLink Aviation Inc. It was flying to Saddam Hussein's hometown of Tikrit from Baghdad's heavily guarded Green Zone, home to Iraq's parliament and many diplomats.

Ereli said the U.S. government routinely hires contractors to provide security for diplomats, facilities or the activities of people connected with the government.

"There is a need for security that goes beyond what employees of the U.S. government can provide and we go to private companies to offer that," Ereli said. "That's a common practice. It's not unique to Iraq. We do it around the world."

Thursday's helicopter crash was thought to be the first shootdown of a civilian aircraft in Iraq since the invasion in March 2003.

On Nov. 22, 2003, a plane operated by the global delivery service DHL was struck by a shoulder-fired missile near Baghdad and forced to make an emergency landing with its wing aflame. The three crew members were unhurt.

It was not the first time Blackwater workers have died in Iraq.

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.

Last year, four Blackwater employees were killed in Fallujah, 40 miles west of Baghdad, and their bodies were burned and mutilated. Two of the corpses were hanged from a bridge over the Euphrates River. The deaths touched off a U.S. Marine assault on insurgents in the city.

This week has seen an increase in insurgent attacks, especially in the capital.

On Thursday, a roadside bomb exploded on the highway leading to Baghdad's airport, severely damaging three SUVs carrying civilians. Police Capt. Hamid Ali said two foreigners were killed and three were wounded. U.S. Embassy and military officials could not confirm the casualties.

In Ramadi, a roadside bomb wounded one soldier in a U.S. convoy. Another American soldier fired his machine gun at a suspected Iraqi ambush site, killing a female Iraqi civilian, U.S. officials said in a statement. Soldiers found an electronic device near the woman that may have been used to trigger the explosion, the statement said.

Hours later, gunfire erupted downtown, and an Associated Press photographer saw the body of a young boy in a street near three smoldering cars.

Sporadic gunfire continued for about two hours, said the photographer, Bilal Hussein. When it subsided, Iraqis pulled the charred body of an adult from one of the burned cars, Hussein said. It was not clear how the two were killed.