Defence Secretary Philip Hammond said he was determined that the rules of engagement were followed in Afghanistan.
He told the BBC's Andrew Marr Show:
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.
I can't comment on the specifics of this case.
We are very determined that rules of engagement will be followed, that any abuse will be dealt with through the normal processes of service justice and that is happening now.
A MoD spokesman said:
The Royal Military Police (RMP) has arrested two further Royal Marines on suspicion of murder in relation to an incident alleged to have taken place in Afghanistan in 2011, taking the total number arrests to nine.
Four Marines have since been released without charge pending further enquiries.
The RMP has referred the cases of the remaining five Royal Marines to the independent Service Prosecuting Authority (SPA). Following direction from the SPA these marines have now been charged with murder and they remain in custody pending court proceedings.
It would be inappropriate to comment further on this ongoing investigation.
Five British Marines have been charged with murder after an incident in Afghanistan in 2011 the Ministry of Defence.
A spokesperson for the Ministry of Defence could neither confirm nor deny reports that a video found on a serviceman's laptop prompted the arrest of seven Royal Marines on suspicion of murder.
An MoD spokesperson has told ITV News the incident involving the marines occurred in the Nad-e-Ali district of Helmand Province during their tour between March and October last year.
They cannot reveal at this stage how the information about the death of an Afghan insurgent came to light.
An MOD spokesperson has outlined the procedure that will take place following the arrest of seven Marines on suspicion of murder.
- The Marines are held in custody under usual civilian custodial regulations. Therefore, if after 24 hours no charges are brought, the Royal Military Police, who are investigating and evidence gathering, will have to apply for an extension of custody.
- The RMP report to the director of service prosecutions, which is part of the services prosecutions authority - the equivalent to the CPS. He is a QC, an independent body and accountable to the Attorney General.
- If there is sufficient evidence they will be charged with murder.
A Ministry of Defence spokesperson has told ITV News the Marines arrested on suspicion of murder are from 3 Commando.
The incident occurred during their tour of Nad-e-Ali.
The incident which led to seven Marines being arrested on suspicion of murder occurred in the Nad Ali district of Helmand, reports Sky News.
The Conservative MP Colonel Bob Stewart has told Daybreak that an insurgent "in these circumstances is someone shooting at one of our soldiers."
He added: "Obviously someone in the military justice system believes that soldiers have broken the fundamental rules of the Geneva Convention".