In all, nine marines were detained in the investigation, but four were released without being charged, while the other five were jailed, the BBC reported.
The Defense Ministry said the incident followed an "engagement with an insurgent" that didn't involve any civilians, while Defense Secretary Philip Hammond told the broadcaster the charges related to rules of military engagement.
"Everybody serving in theater knows the rules of engagement -- they carry cards in their uniforms with the rules on them in case they should need to remind themselves," Hammond said.
Military police began making arrests Friday based on video evidence found by civilian police on a soldier's laptop computer, the report said.
The Royal Marine 3 Commando Brigade served a six-month tour in Afghanistan last year between April and October.
Those charged will face courts-martial, the report said.