The PSNI Chief Constable Mr Hugh Orde has confirmed members of the Provisional IRA were behind the abduction and serious injury of a man in Belfast.
Tensions ran high after police stopped a car at Castle Street in central Belfast with five men on board - one was suffering from serious injuries. Four of the men were arrested and the injured man taken to hospital, said a PSNI spokeswoman.
The injured man is believed to have high-level links to the "Real IRA" and to have been targeted before by the republican movement.
No shots were fired during the arrest, but a large area of central Belfast was sealed off.
"I met with my senior commanders last night and I met them again this morning," Mr Orde told reporters. "What we're talking about was an operation last night by uniformed officers from a local police station, who arrested people who we would say are connected to the Provisional IRA."
The Ulster Unionist Party leader, Mr David Trimble, said the incident "underlines the on-going problem of paramilitarism" in Northern Ireland.," he said.
"The Republican political leadership needs to make it clear as to where it stands and where the Republican movement as a whole stands on such activity," he said.
The SDLP's West Belfast MLA, Mr Alex Attwood, called for an immediate end to all paramilitary violence.
"Whether it is exiling, punishment attacks, recruitment, organised criminal activity and all the rest, the Republican movement must now travel all the way without any delay," he said. "All their criminal activity must end. All violence must stop. There is no basis for a private army and we all need to see this."