Two men were being questioned today about suspected republican paramilitary crimes in Northern Ireland.
The pair were arrested in Bellaghy, Co Derry and taken to the anti-terrorist holding centre in Antrim.
Police would not give details of any alleged offences, or whether the arrests were linked to mainstream or dissident republicans.
Sinn Fein hit out at the arrest operation, and said a complaint had been lodged with the Northern Ireland Police Ombudsman.
Mid Ulster MLA Geraldine Dougan claimed officers continued to search the two men's homes after the early-morning arrests.
"Women and children remain in both houses and the PSNI have refused access to myself and other local representatives," she claimed. "They are refusing to allow the women and children to leave the houses.
"The attitude of the PSNI on the ground is reminiscent of the worst excesses of their disgraced predecessors in the RUC. I have contacted the Police Ombudsman's office to complain about the heavy-handed conduct of this operation."