Five members of the special unit of the British Army (SAS) are under investigation for possible war crimes committed in Syria several years ago, reports the BBC.
So far, no arrests have been made, but the Ministry of Defense's Serious Crimes Unit is investigating.
A number of UK special forces have been deployed to Syria over the past 10 years in operations against Islamic State.
The Ministry of Defense said it was taking allegations of possible crimes seriously.
"All allegations of criminal offenses will be referred to the police for further investigation," a ministry spokesman said.
The investigation is reportedly focused on an incident that occurred two years ago when one of the jihadists was killed.
British soldiers, according to their superiors, used excessive force when arresting the man, but they judged that the jihadist intended to carry out a suicide attack and killed him.
However, the ministry claims that this is not an isolated case and that there are more "terrifying" testimonies about war crimes.
SAS units have been operating in Syria for years, and until a few years ago in Afghanistan.
There has also been an ongoing investigation into whether UK special forces killed civilians and unarmed people in night raids in Afghanistan between 2010 and 2013.
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