BAGHDAD -- Six American civilians were among 11 people killed Thursday when their helicopter was downed north of Baghdad, apparently by hostile fire.

The helicopter's three-man Bulgarian crew and two security guards from an unnamed country were also killed, as Iraq's revitalized insurgency claimed another high-profile success after weeks of reduced activity.

The Americans were contracted to the private security firm Blackwater Security Consulting, and the Russian-made Mi-8 helicopter was operated by a civilian Bulgarian charter company, Heli Air. It was traveling to Tikrit from Baghdad when it was brought down at 1:45 p.m. local time about 12 miles north of the capital, near the insurgent stronghold of Tarmiya, U.S. officials said.

"We presume it was hostile fire that took it down. We don't know what kind of fire and we won't know for sure until there's been an investigation," said U.S. Embassy spokesman Bob Callahan.

A statement issued by the Bulgarian Defense Ministry in Sofia said the helicopter had been "shot by missile fire."

Local television stations showed footage of what they said was the wreckage of the helicopter blazing in a rural area studded with palm trees, and of suitcases and clothes scattered around a wide area. A statement posted on an Islamist Web site claimed the attack in the name of the Islamic Army in Iraq, though the authenticity of the claim could not be verified.

"This is a sad day for the Blackwater family," said a statement issued by Gary Jackson, president of the North Carolina-based Blackwater USA. "We lost a number of our friends to attacks by terrorists in Iraq, and our thoughts and prayers go out to their family members."

In a separate incident, the company said, another Blackwater employee was killed when a bomb exploded beside his armored personnel carrier in the town of Ramadi.

Blackwater is one of the biggest private security contractors working for the U.S. military in Iraq, and the company has lost at least 18 employees since the Iraq war began, including four whose bodies were strung up in the town of Fallujah last April, triggering a bloody conflict for control of the city between U.S. Marines and insurgents.

As road travel has become more perilous, especially outside Baghdad, foreign contractors working in Iraq have increasingly relied on air travel, especially helicopters, to move around the country, even for short journeys. Tikrit is only 100 miles north of Baghdad, about a two-hour drive, but the insurgent-infested route is considered too dangerous to drive.

More than a dozen military helicopters have crashed or been shot down in Iraq, but this would be the first time insurgents downed a civilian aircraft.

The attack coincided with a spike in insurgent activity that has seen an intensification both in the number and the scale of insurgent attacks over the past 10 days.

Three Western security contractors, an American, a Canadian and an Australian, were reported killed when their convoy was attacked by small-arms fire on the dangerous road leading to Baghdad airport, bringing to 17 the number of foreigners killed in Iraq since the weekend.

The attack occurred at noon local time Wednesday, but details were released only yesterday, after the men's families had been informed, said a statement issued by Edinburgh Risk, the British-based private security company that employed them.

The three were identified as James Hunt from Kentucky, Chris Ahmelman from Queensland, Australia, and Stefan Surette from Nova Scotia, Canada.

The group headed by America's most wanted man in Iraq, Jordanian-born Abu Musab al-Zarqawi, claimed responsibility for the Wednesday night attempt on the life of against Prime Minister Ayad Allawi that apparently missed his convoy narrowly as he was returning home from a late night meeting.

"A lion from the martyrs' brigade of the Al Qaeda Organization in the Land of Two Rivers attacked the headquarters of the apostate and ally of the Jews and the Christians after we received information from the intelligence service inside the enemy," the statement said. Two police were killed in the attack.

• Most Read
• Most E-mailed
• Latest News