The dissident republican organisation, calling itself "Óglaigh an hÉireann",has announced a ceasefire with immediate effect.
The development was confirmed at a news conference in Belfast, hosted by veteran trade unionists Peter Bunting and Conal McFeely and Fianna Fáil TD Éamon Ó Cuív.
A statement issued by the dissident group said it was suspending all actions against the British state.
Óglaigh an hÉireann has been one of the most active of the dissident groups.
One of its members, Seamus McGrane, was recently sentenced to 11-and-a-half years in prison after he was convicted of directing terrorism by the Special Criminal Court.
Dissident republican organisation Óglaigh an hÉireann announces ceasefire at Belfast press conference pic.twitter.com/Dg455Dewh6— RTÉ News (@rtenews) January 23, 2018
McGrane, 63, of Little Road, Dromiskin, Co Louth, was convicted in October by the non-jury court of directing the activities of an unlawful organisation, styling itself on the Irish Republican Army, between the dates of 19 April and 13 May 2015.
The court found that McGrane discussed an operation involving explosives in the run-up to the State visit of Prince Charles two years ago.
He was also found guilty by the three-judge court of membership of the IRA between 18 January 2010 and 13 May 2015.
He had denied both charges.
The group also claimed responsibility for that car bomb attack that caused serious injuries to PSNI member Peadar Heffron in 2010.
The group of Dáil politicians involved in ongoing contacts with prisoners groups, includes Maureen O'Sullivan, Clare Daly, Mick Wallace, Thomas Pringle and Mr Ó Cuív.
Mr Bunting told the news conference that he believes the ceasefire announcement is sincere.
Mr McFeely said he believes the statement is clear and unequivocal and should be welcomed. He said the discussions with the group had been challenging and robust, and he was confident the statement indicates an end to their campaign.
Mr Ó Cuív said he had been involved in what has been a painstaking process with the group for two years and he believes today's announcement marks a significant change towards going to a political route.
The move has been welcomed by Tánaiste Simon Coveney, who said the "commitment to a ceasefire with immediate effect is welcome".
Mr Coveney added that "there is no place and no justification for violence".
Outgoing Sinn Féin leader Gerry Adams has also welcomed the announcement, saying "there can be no excuse or justification for the continued existence and operation of armed groups, either unionist or republican".