Garda security chiefs said dissident groups posed a “very real threat” and that their technical capabilities were becoming more “sophisticated”.
Assistant commissioner John O’Mahony, who heads the Garda crime and security branch, said that while the number of dissidents were small, they were “very focused”.
He said that the force’s national security units — led by the Special Detective Unit, assisted by the Security and Intelligence section — had made “significant” inroads.
“During 2015, An Garda Síochána have arrested 31 individuals in connection with dissident republican activity in this jurisdiction,” said Mr O’Mahony, adding that 22 people have been charged before the Special Criminal Court.
He said more than 30 firearms have been seized over the last two years, along with over 1,000 rounds of ammunition as well as explosives, rockets, and mortars.
Samples of the arsenal — including rockets similar to the Kassam ones used by Hamas, as well as AK47s and Semtex — were put on display yesterday at Garda HQ.
Mr O’Mahony said they are concerned dissidents would use the year-long commemoration of the 1916 Rising to launch attacks.
He said: “That is something that is very much in our mind and we will be keeping a very close eye on whether dissidents have any plans around 1916.”
He said gardaí carried out “significant disruption” of dissidents in relation to planned attacks at the time of the visits of Prince Charles in 2015 and Queen Elizabeth in 2011.
He believed “without hesitation” that the dissidents did plan to launch attacks during those visits.
Mr O’Mahony said that young people continue to be recruited into dissident groupings, the main ones being the Real IRA, Óglaigh na hÉireann, and the Continuity IRA. He said young people who were joining did so out of “idealism and peer pressure”.
Gardaí said some of the young people, sometimes just out of college, have talents in technical skills, such as engineering.
Gardaí seized four rockets in one operation in Wexford last year. They said it was the “first time” they had seized such rockets. The two larger missiles were “prototypes” and crude weapons, in that they can’t be targeted apart from changing their degree of trajectory.
In a separate operation, more than one mobile phone which was configured to be used as a detonator was also seized.
Security officers believe dissidents might develop a guidance system to make them more accurate and that obvious targets were PSNI stations and Army barracks.
Gardaí also put on display a beer-keg bomb, together with a timer and an improvised steel booster tube, which was seized in Kilcurry, Co Louth, in May 2014.
Gardaí believe this bomb, captured a few miles from the border, was being delivered to the North to be used in a car bomb.