The PSNI and Garda have vowed to stand together against the dissident republican threat.
A car bomb attack at Palace Barracks, Holywood, last Monday, was deliberately timed to coincide with justice powers being transferred to Stormont.
PSNI Chief Constable Matt Baggott and Garda Commissioner Fachtna Murphy met with new Stormont Minister David Ford and Irish Foreign Affairs Minister Micheal Martin at Stormont yesterday.
Mr Murphy said that the attack on MI5 HQ at Palace Barracks was a reminder that dissidents still had the capacity to do harm. A guardhouse at Newry, Co Down, was damaged following another republican car bomb attack.
Mr Murphy added: “We are working together seamlessly on targeting the individuals, who are a small core of dangerous individuals.”
“Both forces are focused on ensuring a small group of people who intend to do damage have no opportunity to do that.”
The car bomb which exploded on Monday went off as the surrounding area was being evacuated. An elderly man near the barracks at the time was treated for minor injuries.
The device was placed in a taxi hijacked in Ligoniel, about seven miles from Holywood.
The blast came on the day David Ford was elected Northern Ireland's Justice Minister, the first local politician to hold the job in 38 years.
Yesterday, Mr Ford called the attack “a stunt”, adding: “There have been incidents which have happened over the last while, but we have strong evidence of arrests and practical co-operation (between the police forces) ensuring that the terrorists are not succeeding.
He said communications were better between the forces, which Mr Baggott reiterated.
“We have always known that the threat has been severe, we have been developing our capabilities over a number of years to combat that. We have accelerated that over the last number of months,” he said.
“The terrorist threat, the criminal threat from these groups, affects both Northern Ireland and the South.
“It is important that we meet to share communication and technology and speeding up the justice systems to bring them to justice.”