A US Marine and a Navy medic were killed by a US drone strike in April because Marine commanders in Afghanistan mistook them for Taliban fighters, the Los Angeles Times reported Friday.

The two men were the first US military officers to be killed in a friendly fire incident involving unmanned aircraft.

Marine officers on the ground and Air Force crew guiding the drone from a military base in the United States were not aware that analysts watching live video of the firefight from a third location had doubt about the identity of the targets, according to an unpublished Pentagon report cited by the Times.

The April 6 incident in Afghanistan's Helmand province occurred after Marine Staff Sergeant Jeremy Smith, 26, Navy medic Hospitalman Benjamin Rast, 23, and another Marine separated from their platoon and took cover behind a hedgerow as they fired on insurgents in a cluster of buildings nearby.

Though infrared cameras on the Predator hovering above spotted the three men and detected their weapons' muzzle flashes, Air Force analysts watching the video live in Terre Haute, Indiana reported that the gunshots were "oriented to the west, away from friendly forces," or Marines behind the trio, the Pentagon report said.

But the crew controlling the drone from Creech Air Force Base in Nevada and the Marine commanders on the ground "were never made aware" of the assessment, the report added.

"This tragic incident, which resulted in the loss of two dedicated service members, arose from human error during combat with hostile forces. Our military is an organization that learns, and we will honor our fallen by adapting--and by continuing to take the fight to the enemy."

Although he declined to comment directly on the report, Pentagon spokesman George Little told AFP that the "tragic incident... arose from human error during combat with hostile forces."

"Our military is an organization that learns, and we will honor our fallen by adapting -- and by continuing to take the fight to the enemy," he added.