A Covert British army unit which operated in 1970s Northern Ireland gunned down and murdered unarmed civilians with seeming impunity, former members have alleged.

As well as targeting suspected IRA members, it is claimed that the shadowy Military Reaction Force (MRF) also carried out drive-by shootings of nationalists despite there being no independent evidence that they were members of the paramilitary group.

Former members of the unit told the BBC's Panorama programme that they believed they were not subject to military regulations prohibiting firing unless their lives were in immediate danger - known as the yellow card.

One said: "We were not there to act like an army unit, we were there to act like a terror group. We were there in a position to go after IRA and kill them when we found them."

The reaction force had around 40 hand-picked men from across the British army. They operated in west Belfast at the height of the Troubles in the early 1970s but were apparently disbanded after 18 months.

Another ex-member said: "If you had a player who was a well-known shooter who carried out quite a lot of assassinations ... it would have been very simple, he had to be taken out."

Seven former members of the force said they believed the yellow card did not apply to them and one described it as a "fuzzy red line," meaning they acted as they saw fit. Some said they would shoot unarmed targets.

Among those unarmed civilians believed to have been shot by the MRF was Patrick McVeigh, a member of the Catholic Ex-Servicemen's Club who was fatally shot in the back in 1972.

Patrick Corrigan, director of Amnesty International NI, said the charity had long called for an independent investigation into allegations of extra-judicial executions by the security forces in Northern Ireland.

He said that senior police inquiries had been conducted but never fully published.

The revelations underlined the charity's call for a new, mechanism to investigate rights violations and abuse in Northern Ireland which must include those who "pulled the strings."