Five Royal Marines have been charged with murder over a death in Afghanistan last year, Britain's Ministry of Defence said Sunday. They are the first British troops to be charged with murder in the country since deployments began in 2001.

The five are among nine marines arrested — seven on Thursday and two in the last 48 hours. Four have been released without charge.

Officials have said the incident involved an "engagement with an insurgent" in Helmand province, where the majority of Britain's 9,500 troops in Afghanistan are deployed. They say no civilians were involved.

The BBC and other outlets reported that the arrests stemmed from video footage found on the laptop of a British serviceman who had been arrested on an unrelated charge.

The Ministry of Defence said the cases had been referred to the Service Prosecuting Authority, which oversees military trials. The ministry said the suspects, who have not been named, were in custody.

Even though the incident does not involve a civilian, the case could cause a backlash from Afghans and further erode efforts to provide political stability to Afghanistan.

The brigade believed to be involved in the incident, 3 Commando, was in the thick of the fighting with Taliban insurgents during its deployment last year to Helmand, which lies in Afghanistan's south. Seven members of the brigade were killed during the tour of duty between April and October 2011.

British troops operate under rules of engagement, largely derived from the Geneva Convention, that dictate under what circumstances they are allowed to open fire.

"Everybody serving in theatre knows the rules of engagement," Defence Secretary Philip Hammond said Sunday, vowing that "any abuse will be dealt with."

Experts say the military has been strict about enforcing the rules after a disastrous period in Iraq, where there were multiple allegations of torture and abuse by British troops.

The most notorious case involved a hotel receptionist, Baha Mousa, who died while in custody at a British base after being detained in a raid in Basra in September 2003. Britain's defence authorities later apologized for the mistreatment of Mousa and nine other Iraqis and paid a $4.8 million (£3 million) settlement.

Six soldiers were cleared of wrongdoing at a court martial, while another pleaded guilty and served a year in jail.