A nationwide operation was ordered after detectives uncovered a plot to launch a campaign similar to that of the now on-ceasefire IRA.
Starting in the early hours, and co-ordinated from their headquarters in Dublin, police raided addresses in all 32 Irish counties, concentrating particularly on areas close to the Ulster border.
A number of people were held for questioning under the terms of Irish anti-terrorist legislation and documents and other materials were seized.
Suspects connected with Republican Sinn Fein, a group that broke away from the larger Sinn Fein eight years ago, were among those quizzed.
Police believe that a core of hard-line activists was close to the formation of an army council to direct a new IRA-type campaign under the banner of the little-known Irish National Republican Army.
On the second day of his visit to the province - and in the build-up to the summit at Chequers tomorrow with Mr Reynolds - Mr Major said that hopes for peace 'had made a quantum leap forward' following his announcement on Friday that exploratory talks with Sinn Fein will go ahead before the end of the year.
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