Seven Royal Marines have been arrested on suspicion of murder following an incident in Afghanistan in 2011, the Ministry of Defence has said.
The Royal Military Police made the arrests in connection with an incident which occurred after "an engagement with an insurgent", said the MoD.
No civilians were involved and an investigation has now been launched by the Service Justice System.
An MoD spokesman said: "The Royal Military Police have today arrested seven Royal Marines on suspicion of murder. The arrests relate to an incident in Afghanistan in 2011.
"The incident followed an engagement with an insurgent; there were no civilians involved. The investigation will now be taken forward and dealt with by the service justice system.
"These arrests demonstrate the Department and the Armed Forces' determination to ensure UK personnel act in accordance with their rules of engagement and our standards.
"It would be inappropriate to make any further comment while the investigation is under way."