Catholic churches in the diocese of Armagh are making the appeal this weekend in response to a request from the Independent Commission for the Location of Victims' Remains. The commission has set up a confidential phone line and post office box number in the hope of encouraging people to come forward.

There are thought to be nine remaining 'disappeared' from the Troubles, including British army captain Robert Nairac, who is believed to have been killed after going undercover in south Armagh in 1977.

Most are thought to have been killed by the IRA, though in some cases no group has claimed responsibility for their deaths.

Brady has described the issue as "unfinished business from the Troubles" and said his appeal was not a political but a pastoral matter.

The appeal is being published on church notice boards and parish bulletins in Armagh this weekend and is expected to be repeated in other Catholic dioceses in Ireland later this month.

Kenneth Bloomfield, a commissioner on the Independent Commission, said he was "hopeful" that conditions were right for people to come forward, but warned that even if information was given in good faith, it may not prove possible to locate remains.

"These are murders carried out decades ago, probably at dead of night in fairly wild country and on occasions people can give you information which to the best of their knowledge is accurate, but the whole terrain has changed over those decades, " Bloomfield told the BBC.

In 1999, the IRA gave details of nine locations where it said bodies were buried, but the remains of only four individuals were actually found.

Anna McShane, whose father Charles Armstrong went missing in 1981 and is believed to have been killed by the IRA, said families cannot rest until their relatives' remains have been found.

"Before there can be any peace in Northern Ireland, these bodies need to be returned, " she said. "For these families, it is like an ongoing wake, a never-ending wake."