A commercial helicopter has been shot down about 20km (12 miles) north of the Iraqi capital Baghdad, killing all 11 people on board.
Bulgarian sources say a missile brought down the helicopter
Those who died were six US security contractors, three Bulgarian crew members and two Fijian security guards.
US and Bulgarian officials said the Bulgarian-owned chopper was brought down by a rocket-propelled grenade.
It is believed to be the first time a civilian aircraft has been shot down over Iraq since the US-led invasion.
However, insurgents have shot down several US military helicopters.
The Russian-built MI-8 helicopter was owned by a Bulgarian company, Heli Air, and chartered by SkyLink, a North American company.
SkyLink said it had been flying to Tikrit, north of Baghdad.
TV footage showed the burning wreckage of the aircraft in a barren area.
The six Americans who died were working for security contractor Blackwater USA.
Earlier reports said two Filipinos were among the dead, but they were later identified as Fijian.
A leading insurgent group said it had shot down the helicopter, according to a statement published on the internet that could not be verified.
"The Islamic Army in Iraq claims responsibility for bringing down a... cargo aircraft and killing all those on board," said the posting on a website often used by Iraqi insurgents.
The crash came hours after two foreign contractors were killed in a roadside bomb on the road to Baghdad airport.
MAJOR AIRCRAFT LOSSES IN IRAQ
2 Nov 03: US Chinook helicopter shot down near Falluja, killing 16
9 Nov 03: US Black Hawk helicopter comes down near Tikrit, killing six
15 Nov 03: Two Black Hawks collide while trying to avoid ground fire in Mosul, killing 17
8 Jan 04: Black Hawk shot down near Falluja, killing nine
26 Jan 05: US Super Stallion in bad weather near the Jordanian border, killing 31
30 Jan 05: RAF Hercules transport plane comes down near Baghdad, killing 10
Three foreign contractors - an American, a Canadian and an Australian - died in an attack on the same stretch of road on Wednesday.
The same day saw Iraq's outgoing Prime Minister Iyad Allawi escape unhurt after a suicide bomber blew up a car near his convoy in Baghdad. At least two policemen are said to have died in the blast.
Insurgents seem to have stepped up attacks amid delays in forming a new government, the BBC's Jim Muir in Baghdad reports.