Kabul, Afghanistan: An explosion struck Bagram Airfield close to Kabul early Saturday, Nato said, confirming some casualties in an apparent insurgent assault on the largest US military base in Afghanistan.
Abdul Shakoor Quddusi, the head of Bagram district, said three people were killed and 15 others were wounded in the "powerful blast", but could not confirm the nationalities of the victims.
The Afghan defence ministry said it was aware of the explosion but could not immediately confirm the casualties.
No militant group has so far claimed responsibility for the blast, which occurred as the Taliban step up nationwide attacks before the onset of winter, when fighting usually ebbs.
"We can confirm that there was an explosion at Bagram Airfield this morning just after 5:30 am (0100 GMT). There have been casualties," the military coalition said in a brief statement.
"Our Force Protection and medical teams are responding to the situation," it added, without specifying what caused the explosion.
The blast highlights a worsening security situation nearly two years after Nato formally ended its combat operations in Afghanistan, with Afghan forces struggling to rein in
Bagram Airfield, close to Kabul, has frequently come under attack by Taliban insurgents.
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.