A car bomb has exploded close to MI5 headquarters in Northern Ireland today within minutes of policing and justice powers being transferred from London to Belfast.
The explosion happened at the rear of Palace Barracks in Holywood, Co Down, shortly after midnight, police said.
Homes around the base, which houses the MI5 building, were evacuated and residents were taken to the nearby Redburn Community Centre.
Republican dissidents opposed to the peace process were suspected of planting the device, which is not thought to have caused any serious injuries.
Police sources said the bomb was taken to the barracks in a taxi which was hijacked in north Belfast after the cab driver's family was held hostage.
A Northern Ireland Police spokeswoman said: "A device has exploded in a vehicle at the rear of Palace Barracks in Holywood.
"The explosion occurred at approximately 12.24am this morning
"There are no reports of serious injuries at this stage. The incident is ongoing."
Basil McCrea, an Ulster Unionist member of the Policing Board, said one elderly man was taken to hospital after being "blown off his feet".
He said between 50 and 60 people living near the barracks were taken to the Redburn Community Centre in Holywood following a bomb warning.
Mr McCrea said: "The warning was given and the attack alarms went off, but it is obviously a significant device.
"One person, an elderly man, was blown off his feet. I think he was just a member of the community who happened to be walking past. He has gone to hospital. I think it must have been a bit of a shock."
The blast came as law and order policy was returned to Stormont at midnight, marking the end of 38 years of Whitehall control.
It follows a series of attacks by dissidents in Northern Ireland.
In January, PSNI officer Peadar Heffron was seriously injured in an under-car bomb attack in Co Antrim.
This was followed by a car bomb which damaged a court building in Newry, Co Down, in February.
The bomb also comes in the wake of the first anniversary of the deaths of two British soldiers - Mark Quinsey, 23, and Sapper Patrick Azimkar, 21 - who were gunned down by the Real IRA outside Massereene Army barracks in Antrim town in March last year.
Two days later, PSNI Constable Stephen Carroll was murdered by the Continuity IRA in Craigavon, Co Armagh.
Alliance Party deputy leader Naomi Long said the attack appeared to be an attempt to "drag Northern Ireland back into the past".
Cllr Long said: "I would utterly condemn any such attack and am sure that the vast majority of people from across our community are sickened by the actions of people who seem intent on dragging Northern Ireland back into the past.
"It is vital that all local politicians unite to condemn this attack and redouble our efforts to create stable political structures and a peaceful society.
"I would also appeal for anyone with information about this incident to contact the Police so that those behind the attack can be apprehended."