The Apache helicopter was called in for support by ground troops
Nine British troops have been injured in a "friendly fire" incident in Helmand, Afghanistan, the Ministry of Defence has confirmed.
A UK Apache helicopter opened fire on troops from 2nd Battalion The Parachute Regiment on Wednesday after they were "mistaken for the enemy".
One seriously injured soldier was sent back to the UK while two others remain stable at the Camp Bastion base.
Six of the injured have returned to duty. Next of kin have been informed.
The MoD said the accident happened about 1227 local time when a routine British patrol requested fire support when they encountered enemy forces.
"After successfully engaging one enemy position the Apache fired upon another position which the crew believed to be held by enemy forces.
"However, in the confusion of a rapidly changing situation and in, what is, a challenging environment, it would appear that friendly forces were mistaken for the enemy and as a result three members of the patrol were seriously wounded and six more were classified as walking wounded."
An investigation is under way into the incident, the ministry said, adding that "it would be inappropriate to comment until that investigation is complete".