Four Americans have been killed and 17 other people wounded in an explosion at the biggest US military base in Afghanistan.

The Taliban has claimed responsibility for the Bagram Airfield blast, which killed two soldiers and two contractors.

An attacker dressed as a labourer got inside the base with a suicide vest as soldiers took their morning exercise.

Image: The base is one of the most heavily protected military installations in the country

He then blew himself up near a dining area, according to Waheed Sediqi, who speaks for the governor of Parwan province where Bagram is located.

The bomber inflicted "heavy casualties on US invaders", said Taliban spokesman Zabihullah Mujahid.


The explosion, about 35 miles north of the capital Kabul, highlights a worsening security situation nearly two years after NATO formally ended its combat operations in Afghanistan.

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The alliance said: "An explosive device was detonated on Bagram Airfield resulting in multiple casualties.

"Response teams at Bagram continue to treat the wounded and investigate the incident."

The blast follows a suicide attack on the German consulate in the northern city of Mazar-i-Sharif on Thursday night which killed four people and wounded more than 100 others.

Image: Bagram is north of Kabul

The Taliban said the truck bombing was in retaliation for airstrikes near the northern city of Kunduz last week which killed more than 30 civilians.

In December, a motorcycle-riding Taliban suicide bomber killed six US soldiers near the Bagram base, in one of the deadliest attacks on foreign troops in the country last year.

President Barack Obama originally hoped to have all US forces out of the country by the end of his term, but was forced to abandon that goal as Afghan forces struggled to contain the Taliban insurgency.