Five Royal Marines have been charged with murder in relation to an alleged incident in Afghanistan in 2011.
The service personnel remain in custody pending court proceedings.
Seven marines had been arrested on suspicion of murder on Thursday, with a further two arrests on Friday and Saturday.
Of the nine that were arrested in total, four marines have been released without charge, pending further inquiries.
The Ministry of Defence (MoD) spokesman said:
The incident involving the marines occurred in the Nad-e-Ali district of Helmand Province during their tour between March and October last year.
Speaking on the Andrew Marr show Defence Secretary Philip Hammond said: