ROYAL Marine Alexander Blackman, who shot dead an injured Taliban fighter in Afghanistan, will be released from prison on Friday, campaigners said.

The commando, who has spent more than three years in prison for killing the insurgent in 2011, will leave Erlestoke Prison, near Devizes.

He was originally convicted of murder but this was quashed by the Court Martial Appeal Court and replaced with diminished responsibility manslaughter last month.

Five judges ruled that Blackman was suffering from an "abnormality of mental functioning" at the time of the incident, when he was serving with Plymouth-based 42 Commando.

His sentence was reduced to seven years, meaning he could be freed within weeks - a decision his wife Claire Blackman described as "the moment that we have all been fighting hard for".

The Justice for Marine A campaign group had repeatedly posted that the time and date of Blackman's release would not be made public due to "privacy and safety concerns".

But in a statement posted on Facebook on Thursday afternoon, it said: "We are delighted to announce that Al will finally be released tomorrow after what has been a well fought battle by you all.

"We will of course be posting more updates but can we please remember that this is a tense time for the family and that they have asked for some privacy. #justiceformarineA".

The Guardian reported that Blackman will be whisked out of the prison by police in the early hours of the morning.

Writer Frederick Forsyth told the paper: "The establishment wants to spirit him out in the middle of the night to a secret location.

"If I wrote this in a book people would say that's just not the way things are done in Britain. But it is these days."

Blackman was convicted of murder at Bulford Court Martial in 2013 and jailed for life, with a minimum term of 10 years. This sentence was later reduced to eight years.

His wife Claire led a campaign for Blackman to be released.

In March, his conviction for murder was quashed and replaced with manslaughter on the grounds of diminished responsibility.

During the original trial in 2013, Blackman was known only as Marine A.

His identity was made public after his conviction.

A spokeswoman for the Ministry of Justice refused to comment on when Blackman will be released.