A Bulgarian soldier killed Friday was likely shot in "friendly fire" by US troops in Iraq, the Bulgarian Defense Minister said Monday.

Speaking at a news conference, Defense Minister Nikolai Svinarov said the result of an investigation into the fatal shooting "gives us enough grounds to believe the death of rifleman Gurdi Gurdev was caused by friendly fire."

The soldier from the Balkan country was shot dead in a shoot-out with insurgents 45 km south of Bulgaria's base in the central Iraqi city of Diwaniya.

Svinarov said a Bulgarian patrol had fired warning shots in the air in order to halt an Iraqi vehicle.

They then shot back heavily for "someone started shooting at our patrol from the west, and in the same direction, 150 meters away, there was a unit from the US army," said Svinarov.

The Bulgarian soldier became the eighth fatal casualty while serving in Iraq, where the NATO member has about 450 peacekeepers stationed in Diwaniya as part of a multinational force under Polish command.