Seven men have pleaded guilty to charges arising out of a covert MI5 bugging operation against the Continuity IRA (CIRA) in Co Down more than five years ago.
The Head of the PSNI's Serious Crime Branch, Detective Chief Superintendent Raymond Murray, described it as "one of the most significant terrorism cases in recent times".
The men had been due to go on trial next Monday over the undercover eavesdropping operation on a bungalow at Ardcarn Park in Newry in 2014 where CIRA meetings had been held.
At Belfast Crown Court yesterday, the seven defendants were re-arraigned at the request of their defence lawyers on a catalogue of terrorist offences before Mr Justice Colton.
Patrick Joseph 'Mooch' Blair (64), of Lissara Heights, Warrenpoint, Co Down; Liam Hannaway (50) of White Rise, Dunmurry in west Belfast; John Sheehy (35), of Erskine Street, Newry, and Colin Patrick Winters (48), of Ardcarn Park, Newry, all pleaded guilty to charges of belonging or professing to belong to a proscribed organisation.
They admitted providing weapons and explosives training, and conspiring to possess explosives, firearms and ammunition with intent to endanger life. They further admitted conspiracy to possess explosives, firearms and ammunition with intent, along with preparing acts of terrorism.
Blair, Hannaway and Winters also admitted collecting information likely to be of use to terrorists. Sheehy further pleaded guilty to attending a meeting at Ardcarn Park for the purposes of terrorist training. Winters also admitted to allowing his Ardcarn Park home to be used for the purposes of a terrorist meeting.
Seamus Morgan (64), of Barcroft Park, Newry; Kevin John Paul Heaney (46), of Blackstaff Mews, Springfield Road in west Belfast, and Terence Marks (49), of Parkhead Crescent, Newry, all pleaded guilty to belonging or professing to belong to a proscribed organisation. Marks also admitted a further charge of receiving training in the making or use of explosives for terrorism.
All of the offences took place on dates between August 11, 2014 and November 11, 2014.
Mr Murray said: "This is one of the most significant terrorism cases in recent times given the seriousness of the offences and the number of people involved.
"Today's result demonstrates our commitment to disrupting terrorism and protecting the community."
Counsel for Hannaway said he would be submitting a number of medical reports to the court relating to his mental and physical health problems.
Mr Justice Colton said he would release all seven defendants on continuing bail.
He set the date for a plea and sentencing hearing for Wednesday, March 25.
No details were given in court yesterday about the background to the charges the seven defendants pleaded guilty to.
But a previous court hearing in 2014 heard that police believed Winters' home at Ardcarn Park was being used to host meetings of the Continuity IRA.
MI5 had gained access to the property and planted secret listening devices in a number of rooms in the property to record conversations at the meetings.
The court heard that suspects in the property had been recorded discussing potential targets for attack, including specific police officers.
Potential attacks against judges were also discussed, along with weapons training, funding for terrorist activity and plans to get weapons, a prosecution lawyer added.
A PSNI detective involved in the case told the court the suspects were "leading key figures of a proscribed organisation".