Two US soldiers in Afghanistan 'killed in attack by Afghan army commando'

Two US soldiers in Afghanistan have died and a further two were wounded after a colleague from the Afghan army opened fire on them, an official has reported.

The Afghan commando who launched the attack also died, said a spokesman for the Nangarhar provincial governor.

The incident took place in the eastern Achin district, where US specialforces have been fighting alongside Afghan troops against Islamic State and Taliban militants, the spokesman said.

"The cause of the shooting is not clear. An investigation has already begun," he said.

A spokesman for the U.S. military command in Kabul said they were aware of the report but could not yet confirm any details.

The Taliban claimed they were behind the attack and the Afghan soldier had been a supporter of the group.

Insider attacks have happened before in Afghanistan.

In March, another Afghan soldier was killed after he opened fire on foreign forces at a base in Helmand province, wounding three US soldiers