A blast has reportedly hit a NATO convoy in eastern Afghanistan, killing at least nine troopers including five American soldiers.

On Wednesday, five US troops and four Afghan soldiers were killed in the blast that hit near a US military base in the eastern province of Khost.

The US military has confirmed the deaths and says the cause of the blast is still under investigation. The Taliban have claimed responsibility for the attack.

More than 506 foreign forces were killed in Afghanistan this year, 310 of which were US troops.

The United States currently commands over 110,000 US and foreign troops in Afghanistan and plans to deploy another 40,000 soldiers to the Central Asian nation.