Image caption Former SAS sergeant Colin Maclachlan has appeared on the Channel 4 show SAS: Who Dares Wins

A former SAS sergeant has said he is being investigated for murder after admitting he shot dead enemy fighters in what he called a "mercy killing".

Colin Maclachlan, 42, from Edinburgh, wrote in a new book about how he had killed "two or three" mortally wounded enemy soldiers in Iraq in 2003.

Killing mortally wounded soldiers is against British military law and the Geneva Convention.

The BBC understands military police are carrying out a preliminary probe.

The Ministry of Defence (MoD) has declined to comment.

'Pleading'

Sgt Maclachlan said the killings took place on the Syrian border in March 2003, where an SAS squad fired rockets at enemy units. After the attack Sgt Maclachlan discovered two Iraqi soldiers who had been disembowelled and another who had lost three limbs.

Sgt Maclachlan, who appeared on the Channel 4 programme SAS: Who Dares Wins, said the injured soldiers were "pleading for us to do it".

He wrote: "Special Forces operatives quickly put them out of their misery, rather than leaving them to die slowly and in agony."

It is part of a new book called SAS Who Dares Wins: Leadership Secrets From The Special Forces.

Speaking to the Mail on Sunday, the former soldier said he was informed of a military police investigation by email.

He added: "Our motives were entirely humane. I'll happily go to court, I'll happily go to jail, if you think I've done wrong. But people should put themselves in my position first. Walk around in my boots, then judge me."

Although the MoD would not comment on Sgt Maclachlan's case specifically, a spokeswoman said: "Credible allegations of criminal behaviour will always be investigated properly."