BAGHDAD, April 21: Guerillas in Iraq shot down a Bulgarian commercial helicopter on Thursday and all nine people aboard were killed in what was believed to be the first downing of a civilian aircraft in the country. The Russian-built Mi-8 helicopter was shot down by a rocket-propelled grenade, Bulgaria’s Defence Ministry said.

The attack north of Baghdad came amid a surge in violence and puts further pressure on Iraq’s leaders as they struggle to form a government nearly three months after elections.

The helicopter was flying near the town of Tarmiya, about 40km north of Baghdad, when it was hit, US military sources said, adding all aboard were civilians.

An official said the passengers were of mixed nationalities.

Meanwhile, an American, an Australian and a Canadian were killed on Wednesday in an attack on their convoy on the Baghdad airport road, a statement from their employer said on Thursday.

They were killed when vehicles in their convoy “were attacked by insurgents using small arms fire,” the Edinburgh Risk security firm said.

POLITICAL DISPUTE: The attack came amid a surge in insurgency over the past two weeks, threatening to eclipse efforts by elected leaders to form a government, amid growing tensions between Iraq’s majority Shia and once-dominant Sunni Muslim communities.