Two Americans — a serviceman and contractor — were killed Wednesday when a gunman in an Afghan army uniform opened fire near Kabul, officials said.

The killer also wounded three others — one soldier and two civilians — before he was fatally shot, authorities said.

“The two individuals were killed during an attack near a coalition base by an unknown assailant who was later killed,” according to a statement from US military commanders.

“They were conducting duties as part of the larger NATO mission to train, advise and assist the Afghan security services.”

The shooting happened at about 11 a.m. (3 a.m. New York time) at a checkpoint near a military ammunition supply point, senior defense officials told NBC News.