°®Âþµº

At least four people died when a Taliban suicide bomber posing as a labourer detonated explosives at the largest US base in Afghnistan.

The four dead included two soldiers and two contractors all from the US, in the huge blast carried out by a suicide bomber. 

The Taliban claimed responsibility for the blast inside the heavily fortified Bagram Airfield, north of Kabul, which injured another 17 other troops, including a Polish serviceman.

It comes as the Taliban wind down the summer offensive, with winter usually seeing a downturn in attacks by the insurgents.

The nationalities of those killed and wounded were not immediately known after the explosion.

"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.

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

Surprise attack

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.

"We don't know the identity of victims yet but the attacker was one of the Afghan labourers working there," Sediqi told AFP.

Bagram district governor Abdul Shakoor Quddusi described the explosion as "powerful", saying it reverberated across the area.

The US has around 10,000 troops in Afghanistan, with the largest contingent stationed at the Bagram base.

We don't know the identity of victims yet but the attacker was one of the Afghan labourers working there. - Waheed Sediqi, Afghan government

The brazen attack represents a major security breach inside what is regarded as one of the most heavily guarded military installations in Afghanistan.

"To the family and friends of those who lost their lives today, we share your loss and our thoughts are with you. We offer you our deepest condolences," said John Nicholson, the top US and NATO commander in Afghanistan.

Growing threat

The attack highlights the increasing reach of the Taliban, with government forces struggling to contain the militants.

Taliban spokesman Zabihullah Mujahid said the insurgent group was behind the suicide attack inside Bagram, claiming it inflicted "heavy casualties on US invaders".

Bagram Airfield has frequently come under attack by Taliban insurgents.

Last December, a motorcycle-riding Taliban suicide bomber killed six US soldiers near the base in one of the deadliest attacks on foreign troops in the country in 2015.

The latest assault came after a powerful Taliban truck bomb struck the German consulate in Afghanistan's northern Mazar-i-Sharif city late Thursday, killing at least six people and wounding more than 100 others.

The uptick in attacks against Western targets comes just days after a bitter US presidential election.

Afghanistan got scarcely a passing mention in the election campaign - even though the situation there will be an urgent matter for the new president.

President-elect Donald Trump is set to inherit US' longest war with no end in sight.