A number of U.S. and Afghan forces have sustained casualties in an apparent so-called "green-on-blue attack" late Saturday, an official confirmed.

Col. Sonny Leggett, spokesman for U.S. forces in Afghanistan, confirmed the incident in a statement.

"A combined U.S. and Afghan force conducting an operation in Nangarhar province was engaged by direct fire on Feb. 8," he said, adding casualties were suffered in the attack.

“We are assessing the situation and will provide further updates as they become available,” he added.

The so-called "green-on-blue-attack" means attacker/s, wearing Afghan forces' uniform, attack foreign/American troops.

The NATO forces in Afghanistan last month confirmed two U.S. service members got killed in the plane that “crashed” in Ghazni province.

This came as Taliban insurgents on Jan. 27 claimed to hit down the plane, allegedly belonging to the CIA.

Earlier, on Jan. 11, at least two U.S. service members killed and two others wounded when their military convoy vehicle struck an improvised explosive device in restive southern Kandahar province, the NATO's Resolute Support mission statement said.

Last year, according to non-classified figures by the NATO mission, at least 20 U.S. soldiers got killed in Afghanistan.