Seven Royal Marines have been arrested on suspicion of murder following an incident in Afghanistan last year, the Ministry of Defence said.
The Royal Military Police made the arrests in connection with an incident which occurred after "an engagement with an insurgent", the MoD said.
The rules of engagement, largely derived from the Geneva Convention, dictate under what circumstances British troops are allowed to open fire, whether that is to prevent an attack by the enemy or in direct contact.
The arrests are thought to be the first time UK servicemen have been held on suspicion of such charges during the conflict in Afghanistan.
Five Royal Marines have been charged with murder in relation to an alleged incident in Afghanistan in 2011.
Military police have arrested seven Royal Marines on suspicion of murder over an incident in Afghanistan, the Ministry of Defence has said.