The PSNI and Garda Special Detective Unit have targeted suspected senior members of the New IRA in a series of raids on both sides of the border.
The operation began at dawn yesterday.
Multiple searches were linked to leading dissident republicans in Northern Ireland, where there were nine arrests, with six searches being carried out in the Republic, which resulted in no arrests.
In Dublin, senior sources said one of those targeted by the SDU is a 53-year-old north inner-city criminal, who has a previous conviction for handling stolen property and has been a major target for specialist gardaí for years.
Another of those targeted in the capital is a 59-year-old man, who was previously jailed at high security Portlaoise Prison for IRA membership. He also has a previous conviction for being involved in an armed robbery.
The six searches by gardaí were carried out in counties Dublin, Cork, Laois and Kerry.
The 10 arrested in Northern Ireland are being held under the Terrorism Act.
Properties were raided in Derry, East Tyrone and Belfast.