DUBLIN (Reuters) - Ireland freed from 40-year prison terms three IRA men who killed policemen in the 1980s, provoking fury from police groups and the son of one of the victims. Supporters of the prisoner release programme argue it is a crucial pillar of Northern Ireland`s peace accord. They say it helps build trust with armed groups and ties them to their truces after a bitter conflict waged by pro-British Protestants and pro-Irish Catholics that killed more than 3,600 people. "While we are conscious of the hurt involved for the bereaved families, today`s releases will see these men re-united with their families having served long periods of time in jail," said Martin Ferris of Sinn Fein, the Irish Republican Army`s political wing. But some politicians and relatives have sharply criticised the process - including the family of Seamus Quaid, who was shot dead in 1980 by Peter Rogers, one of those released on Tuesday. They expressed their grief in an interview this week with Mark Costigan of Dublin radio station Today FM. The release of the three men and later release of a fourth IRA man convicted of killing a policeman will bring the number of guerrilla prisoners released in the Irish Republic to 16, a justice department spokesman said. In British-ruled Northern Ireland, more than 200 members of armed groups have been freed since the accord in April offered amnesties to members of guerrilla groups observing ceasefires. Ireland is freeing other IRA prisoners temporarily over Christmas, including four men who held a couple hostage for six days in London`s Balcombe Street in 1975. Opposition politicians in London have urged the British government to stop freeing prisoners until the groups involved start disarming - especially since the IRA has given no signal when, if ever, it will start handing over weapons. The peace deal only specified a May 2000 completion date for the process. Though the IRA won most notoriety for its bombing campaign elsewhere, it also attacked banks and post offices inside the Irish Republic to raise funds for its battle to unite the island and free Northern Ireland`s Catholic minority from British rule.