Two US troops killed by Afghan soldier in Nangarhar attack

Two American troops were killed and six others wounded when an Afghan soldier armed with a machine gun opened fire, the US military confirmed Sunday.

The incident occurred late Saturday in Nangarhar province in eastern Afghanistan when US and Afghan commandos were conducting a "key-leader engagement" at a base in Sherzad district.

"Current reports indicate an individual in an Afghan uniform opened fire on the combined US and Afghan force with a machine gun," US Forces-Afghanistan spokesman Sonny Leggett said in a statement on Sunday.

Provincial governor Shah Mahmood Meyakil said in an audio message to reporters that three Afghan commandos were wounded.

He said it was not immediately clear if the incident was a deliberate act by an "infiltrator" or an accident.

"It was not a clash between the forces. We are investigating," Meyakil said. Leggett also stressed the cause or motive behind the attack were not immediately known.

In a tweet, the US Army's 7th Special Forces Group (Airborne) said "several" of its soldiers had been killed or injured during combat operations in Afghanistan.

No group immediately claimed responsibility.

Last year was the deadliest for US forces in Afghanistan since combat operations officially finished at the end of 2014, highlighting the challenging security situation that persists.

In December, Taliban infiltrators in the Afghan military killed nine Afghan soldiers in central Afghanistan.

In July, an Afghan soldier killed two US troops as they were visiting an Afghan army base in Kandahar.

That came two weeks after another Afghan soldier shot and killed an influential Afghan army colonel while he was conducting a security assessment in Ghazni province.