IRA killers who gunned down 10 Protestant workmen in one of Northern Ireland's worst atrocities were ordered to finish off their victims as they lay injured on a roadside, a report has revealed.

The victims were lined up before the gunmen and the intention was that nobody was to survive, a report into the massacre near the Irish border 35 years ago said.

Up to 11 gunmen were involved in the slaughter at Kingsmills in Co Armagh. Their weapons may be linked to around 100 other killings.

Families of the victims called for a public inquiry and answers from republicans as the report was released by the Historical Enquiries Team (HET).

On January 5 1976 the 10 textile workers were travelling home from work in the dark and rain in a minibus in the heart of rural Co Armagh when they were ambushed. They allowed the only Catholic to go free. The rest were lined up against the minibus. Only one man, Alan Black, survived but he suffered 18 gunshot wounds.

The report concluded that the Provisional IRA was to blame for the killings, even though that organisation denied it and was supposed to be on ceasefire;

It was a planned attack on a target that had been selected and researched some time before, and earlier loyalist attacks on other families were the catalyst for the premeditated and calculated slaughter.

The motive was sectarian, the report said, with each man murdered because he was a Protestant. This was underlined by the fact that the only Catholic worker in the group, Richard Hughes, was allowed to get away;

At least 11 weapons were used, suggesting that up to 11 gunmen were involved. The report said: "After the initial burst of heavy gunfire, it became apparent to the gunmen that some of the workmen may still be alive. The intention to murder everyone was absolute. No one was to survive."

The report added that Mr Black described how a further command was given to finish off the victims. "Another burst of concentrated gunfire was fired into the heaped bodies of the workmen as they lay on the roadway," it added.