4 Americans killed in US base attack

Four Americans were killed yesterday in a suicide bombing inside the largest US military base in Afghanistan, Pentagon chief Ashton Carter said, in a major breach of security.

The Taliban claimed responsibility for the bombing inside the heavily fortified Bagram Airfield, north of the capital Kabul, which left 16 other US service members and a Polish soldier wounded as the insurgents ramp up attacks on Western targets.

The dead included two American soldiers and two contractors, in an assault which highlights rising insecurity in Afghanistan nearly two years after US-led Nato forces formally ended their combat operations.

The blast was caused by a suicide attacker who blew himself up near a dining facility inside the base, said Waheed Sediqi, spokesman for the governor of Parwan province where Bagram is located.

"The attacker was one of the Afghan labourers working there," Sediqi told AFP.

Bagram district governor Abdul Shakoor Quddusi described the explosion around 0100 GMT as "powerful", saying it reverberated across the area. The base was put on lockdown following the attack.

The attack represents a brazen security breach inside one of the most heavily guarded military installations in Afghanistan. The United States has around 10,000 troops in Afghanistan, with the largest contingent stationed at the Bagram base.

The base is enveloped by multiple layers of Afghan and American guards, security cameras and watch towers, and a surveillance blimp keeps a close watch on the surrounding areas.