Image copyright Getty Images Image caption Michael Collins had ordered the continuation of covert actions in Northern Ireland.

Attempts were made to cover-up details about the murder of six Protestants in County Armagh in June 1922 by the IRA, newly released files have shown.

Around 30 IRA men from County Louth crossed the border to attack the community of Altnaveigh, near Newry.

Five men and one woman were killed, and more than a dozen properties were also burned down or bombed.

The files were released by the Republic of Ireland's Military Service Pensions Collection.

Details on the files' contents emerged in a report in the Irish Examiner.

The killings, that became known as the Altnaveigh Massacre, were one of the most controversial IRA attacks of the period.

Protestant communities were left in fear following the violence, which was seen by some as an attempt to ethnically cleanse the area.

Among those who were killed were John Heaslip and his teenage son Robert, and Thomas and Elizabeth Crozier, a couple who were said to have been targeted because they recognised the attackers.

The murders occurred following the signing of the Anglo-Irish Treaty but Michael Collins had ordered the continuation of covert actions in Northern Ireland.

The details are contained in newly released files which cover the claims for military pensions of several men who were there.

Reprisal attacks

According to Irish state broadcaster RTÉ, an IRA brigade report from the time has a section entitled "Altnaveigh shootings" but the details are left blank.

Other files simply refer to a "special job".

Nine men in total are named in the files as having participated.

One of the men involved, James Marron, said the unit was under orders to "burn every house and shoot every male".

It is believed that the murders were either carried out as a reprisal for the killings of local Catholics or of IRA men by B Specials, and according to Marron, Altnaveigh was chosen because it was a "stronghold of the B Force Murder Gang".

The records show that Marron reported suffering from a psychological disorder following the attack, while others who took part left Ireland.

"For a long time I could not sleep thinking of the woman and the others we shot," he said.

'We knew the people'

According to the Irish Examiner, in 1941, during an appeal against the pension he had been awarded, Marron said that Mick Fearon, who led the operation, had previously told him not to let anything be put in writing about Altnaveigh.

"We had a talk over it and we came to the conclusion, that if it was ever known, that our lives would be in danger. And we had no guarantee that it would not be known," wrote Marron.

"We knew the people and saw them every day. We were well disguised on the job and are not known as yet to have been on it, that was the main reason why we gave as little information as we could."

Another of those involved, Thomas Kinney, stated that he "carried out reprisals at Altnaveigh for murder of the four IRA soldiers", while Patrick Loughran said that "on the night of the reprisal, we attacked and practically cleaned out all the armed B men in the district."

A further man whose name has been linked to the killings is Frank Aiken, who was commander of the IRA's Fourth Northern Division, which operated in Armagh, south Down and north Louth.

He was named by one man as being present, but archivist Rob McEvoy believes Aiken was involved in a different ambush that same night.

However, it is accepted that given his position as divisional commander, he would had to have given his approval for the Altnaveigh attack.

Aiken, who died in 1983, was a prominent Fianna Fáil politician who served as a minister in various Irish governments.