Five Royal Marines have been charged with murder in relation to an incident in Afghanistan in 2011.

Seven were arrested last week and the Ministry of Defence (MoD) said Royal Military Police (RMP) had arrested two more Marines on suspicion of murder. One was held on Friday and the other yesterday, taking the total number of arrests to nine.

Four have since been released without charge.

The MoD said: "The RMP has referred the cases of the remaining five Royal Marines to the independent Service Prosecuting Authority. These Marines have been charged with murder and they remain in custody."

Defence Secretary Philip Hammond said he was determined that the rules of engagement were followed in Afghanistan.

He said: "Everybody serving in theatre knows the rules of engagement, they carry cards in their uniforms with the rules on them. I can't comment on the specifics of this case."

Meanwhile, Mr Hammond said former military chiefs could be barred from contact with ministers and Ministry of Defence officials after several were secretly filmed claiming to be able to help secure lucrative contracts for arms firms.

Among those targeted were Lieutenant General Sir John Kiszely, ex-head of the Defence Academy and now Royal British Legion president, and former head of the Army Lord Dannatt. All deny breaking any rules.