Three people have been arrested after arms and explosives - including half a kilo of Semtex - were discovered during a house raid in west Belfast on Friday.
A 21-year-old woman and a 29-year-old man are being questioned at a police station in Antrim in Northern Ireland.
A 45-year-old man has been arrested in Sunderland.
Police said the operation was part of an investigation into "violent dissident terrorist activity".