Even as the British army was still reeling from allegations of misconduct by its troops in Iraq, seven Royal Marines, who served in Afghanistan, were arrested on suspicion of the murder of a Taliban militant.

The Ministry of Defence said the arrests related to an incident that followed an “engagement with an insurgent” in Helmand last year. It said no civilians were involved.

Elite unit

All those arrested belonged to the elite 3 Commando Brigade, rated highly for its record in Afghanistan until now. According to media reports, the incident came to light accidentally after the Royal Military Police, investigating a case involving pornographic material, found footage on a laptop showing a group of soldiers huddled around an injured man lying on the ground. The man later died.

The MoD declined to give details saying it would be “inappropriate to make any further comment while the investigation is under way”.

“The investigation will now be taken forward and dealt with by the service justice system. These arrests demonstrate the Department and the Armed Forces’ determination to ensure U.K. personnel act in accordance with their rules of engagement and our standards,” a spokesman said.

The Afghan Defence Ministry said the incident highlighted the need for NATO forces to respect the laws of war.

“One of the reasons for high numbers of civilian casualties is that foreign troops and others are careless,” a spokesman said.

Defence observers said the case could have a serious impact on the army’s reputation.

“There is no doubt about it, this is politically damaging because we’re not talking about an individual case here. Last year, there was a case of a soldier shooting someone and a soldier stabbing someone — those are individual cases and you will get that just on the law of averages in combat zones. But this is seven people, a unit, a group of marines who are very highly trained,” Professor Michael Clarke, director general of the Royal United Services Institute, told the BBC.

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