NATO says at least four people have been killed in an explosion inside the largest US military base in Afghanistan, with the Taliban claiming responsibility for the attack.
The explosion struck at dawn on Saturday inside the heavily fortified Bagram Airfield, north of Kabul, as the Taliban step up attacks on Western targets before the onset of winter, when fighting usually ebbs.
The nationalities of those killed were not immediately known after the blast, which highlights a worsening security situation nearly two years after NATO formally ended its combat operations in Afghanistan.
"An explosive device was detonated on Bagram Airfield resulting in multiple casualties. Four people have died in the attack and approximately 14 have been wounded," NATO said in a statement.
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"Response teams at Bagram continue to treat the wounded and investigate the incident."
Waheed Sediqqi, spokesman for the Parwan provincial governor, said the bomber managed to enter the heavily protected site and was standing in a queue with Afghan labourers when he detonated a suicide vest.
Bagram Airfield, close to Kabul, has frequently come under attack by Taliban fighters.
Al Jazeera's Abdullah Shahood, reporting from Kabul, said the base is in a heavily guarded area where people only with exclusive access can enter.
"An Afghan police official told us that the person who got in with the explosives must be a dual citizen and someone who has an access pass and is trusted to go without escort," he said.
The explosion underscores a worsening security situation nearly two years after NATO formally ended its combat operations in Afghanistan.
The US currently has around 10,000 troops in Afghanistan, with the largest contingent stationed at Bagram Airfield.
Last December, a motorcycle-riding Taliban suicide bomber killed six US soldiers near Afghanistan's largest US military base.
It was one of the deadliest attacks on foreign troops in the country in 2015.
On Thursday, four people were killed and 128 others were wounded when a suicide bomber drove a lorry loaded with explosives into the German consulate in the northern city of Mazar-e Sharif.
Source: News Agencies