LONDON, (Reuters) – British military police have arrested seven soldiers on suspicion of murder, the defence ministry said on Thursday, following what it said was an “engagement” with an insurgent last year in Afghanistan.

“The Royal Military Police have today arrested seven Royal Marines on suspicion of murder. The arrests relate to an incident in Afghanistan in 2011. The incident followed an engagement with an insurgent: there were no civilians involved,” the ministry said in a statement.

The defence ministry gave no further details.

Relations between Western forces and Afghan civilians have been strained in the last year after soldiers burned copies of the Koran at a NATO base and a U.S. soldier was accused of killed 16 civilians in a rampage in March.

A video also emerged depicting U.S. marines urinating on corpses.

Relations between Western troops and Afghan forces have also deteriorated after a series of “insider” attacks against NATO coalition troops by Afghan soldiers or by militants wearing Afghan military uniform.