A car bomb exploded near to the headquarters of MI5 in Northern Ireland on Monday 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."
