US soldiers die in Afghan crash

US troops are deployed in remote regions

A United States military helicopter has crashed in Afghanistan killing five American soldiers.

Seven others were injured in the crash near Bagram air base, US Central Command said in a statement.

"The cause of the crash is unknown and under military investigation," the statement said.

Helicopters from the Bagram base have been used as part of a US offensive against suspected al-Qaeda and Taleban members in remote areas of the country.

Operation Mountain Resolve is aimed at destroying bases used by militants linked to al-Qaeda and other groups in the wild region of Nuristan and Kunar.

The Central Command statement said the troops aboard the downed helicopter were supporting Operation Mountain Resolve.

US war planes are also involved, called in by the troops on the ground.

But the US military has found it hard to locate al-Qaeda, the BBC's security correspondent Frank Gardner says.