Police arrested three men today for questioning about paramilitary activity by dissident republicans opposed to the peace process.
They were detained in Strabane, Co Tyrone, where three homes were also searched.
The arrests followed the discovery earlier this week of explosive devices near a pub four miles outside the town on the main road to Derry, and at a house near Newtownstewart, Co Tyrone.
Police said the three men were being questioned by detectives at Antrim.