Six die in US helicopter crash

An American Black Hawk helicopter has been forced down near Saddam Hussein's hometown of Tikrit, killing all six soldiers on board.

The US military is investigating whether the chopper was attacked or suffered mechanical problems.

American troops have secured the scene near the Tigris River in north Iraq.

Last weekend, an American Chinook helicopter was shot down, killing 16 soldiers in the biggest single strike on US forces since they invaded Iraq.

The Black Hawk went down on a riverbank along the Tigris River about a kilometre from the US base in Saddam Hussein's former palace in Tikrit.

Smoke was seen rising from the wreckage as other helicopters hovered above.

"We don't know if it was a mechanical failure or hostile fire," Major Josslyn Aberle told the Associated Press.

All the soldiers killed were from the 101st Airborne Division.

On 25 October a Black Hawk helicopter was shot down near Tikrit, injuring one crew member.

Tikrit lies in the heart of the "Sunni Triangle" - the region around Baghdad seen as most loyal to the ousted regime of Saddam Hussein.

It has been the scene of continued resistance to US-led forces.

In continuing violence elsewhere, a US convoy was ambushed in Mosul early on Friday morning, coming under fire from small arms and rocket-propelled grenades, the US military said.

One soldier died and six others were injured in the clash.

This brings the number of US soldiers killed in action since President George W Bush declared major combat over on 1 May to 140.

In a separate attack, a roadside bomb in the city injured three US soldiers.

Mosul, Iraq's third largest city and close to the semi-autonomous Kurdish areas, was quiet until relatively recently.

Correspondents say the spate of attacks there has prompted concern among US commanders that guerrilla attacks are spreading north from the Sunni Triangle.

Chinook warning

The attack came hours after a memorial service was held for the men killed when their Chinook helicopter was shot down on Sunday.

"Death was in the cause of freedom. They were serving our country and answering our nation's call to fight terrorists," Colonel David Teeples, commanding officer of the men's unit, said.

Army officials said the Chinook's crew apparently had a warning of an approaching missile seconds before it struck, the Associated Press reports.

The crew managed to launch flares designed to draw the heat-seeking missile away but the defensive measure did not work.