More than 40 people were detained under emergency anti-terrorism laws in the last year, figures reveal.
In addition to these arrests, conducted under 1998 laws, over 100 people were detained in the same period under the State's foundation 1939 anti-terror legislation.
Some 13 people have been convicted of terror offences in the last 12 months and a further 34 are awaiting trial.
In a report renewing emergency powers in the Offences Against the State (Amendment) Act 1998, Justice Minister Charlie Flanagan said dissident republican groups pose a “real and persistent threat”.
He said this was “evidenced tragically” by the murders of PSNI prison officers, attempted murders of PSNI constables and the recent murder of young journalist Lyra McKee in Derry.
The minister said the small number of people supporting jihadist extremism was a “cause for concern” and that their activities were monitored “very closely”.
The 1998 Act was enacted in the wake of the slaughter of 29 people, including a mother of twins, by the Real IRA in Omagh on August 15 that year.
The Act, which amended the earlier Offences Against the State Acts, contains provisions which change the rules of evidence in relation to the offence of membership of an unlawful organisation, create certain new/substantive offences and extend the maximum period of detention under section 30 of the 1939 Act.
The Act also contains a provision that certain sections would cease to be in operation unless the Oireachtas passes resolutions to continue for a further period.
In his report to the Oireachtas, covering the period June 1, 2018 to May 31, 2019, the minister said:
There has been a massive increase in detentions in the last 12 months under Section 7 of the 1998 Act, relating to possession of articles for purposes connected with the commission, preparation or instigation of an offence.
The numbers have gone from two in 2016, to 24 in 2017, to zero in 2018 and up to 66 in 2019.
There has been a substantial drop in detentions under Section 2 of the 1998 Act, relating to the drawing of interferences from an accused's failure to answer questions relating to the offence of membership of an unlawful organisation.
The numbers have dropped from 68 in 2016, to 31 in 2017, to 21 in 2018 and to three in 2019.
Minister Flanagan said the “primary security threat” was from dissident republicans: “There remains a real and persistent threat from these groups.
He said: “The dissident paramilitary groups continue to focus their efforts primarily on targeting members of the security forces in Northern Ireland, as evidenced tragically in recent years by the murders of NI Prison Officers, and a number of attempts to murder PSNI constables.
"This year also saw further tragedy with the appalling murder of a young journalist in Derry.”
He said Ireland could not consider itself immune from international, jihadist-type terrorism and extremism, though an attack here was “considered unlikely”.
But he added: “There is a small number of people here whose activities in support of extremism gives cause for concern and the authorities monitor their activities very closely.”