Five Royal Marines have been charged with murder over an incident in Afghanistan in 2011, the MoD has said. It says nine marines were arrested over the incident, involving an insurgent. Four have been released without charge.

The five charged remain in custody, and the next stage of the process is likely to be trial by court martial. The marines were arrested by the Royal Military Police after suspicious video footage was found on a serviceman's laptop by civilian police in the UK.

The charges are related to an incident in Afghanistan last year, when Royal Marine 3 Commando Brigade was based in Helmand. The MoD previously said the incident followed an "engagement with an insurgent" and no civilians were involved. It is believed to be the first time UK servicemen have been arrested and charged with such charges during the Afghanistan conflict.

The Service Prosecuting Authority (SPA), an independent body that conducts prosecutions on behalf of the military, decided the five should face murder charges. Speaking on the BBC's Andrew Marr Show, Defence Secretary Philip Hammond did not comment on the specifics of the case but insisted the MoD was "determined that rules of engagement" be followed.

He added: "Everybody serving in theatre knows the rules of engagement, they carry cards in their uniforms with the rules on them in case they should need to remind themselves." During a six-month tour of duty, which lasted from April to October last year, seven servicemen from 3 Commando Brigade were killed in action, all from 42 Commando.

A court martial is a public court with similar powers to a crown court. It can impose prison sentences, fines or other forms of justice depending upon the nature of the crime. They are presided over by a judge advocate and a board of up to seven lay members, individuals with no legal training much like a jury in civilian courts.

The MoD said it would be inappropriate to comment further on the ongoing investigation.