Police in Northern Ireland say they have thwarted "a number of murder attempts" since last Friday's van bomb in Belfast.

Officers had warned that other dissident republican attacks were likely after a booby-trap bomb exploded beneath a prison officer's van.

The 52-year-old escaped with leg injuries but police chiefs remain concerned about the capability of those who violently oppose the peace process.

Assistant Chief Constable Will Kerr, Police Service of Northern Ireland, said: "They've shown their capability to construct and use a wide range of IEDs, improvised explosive devices, whether under vehicle, whether, rocket propelled, whether it’s remote control detonated by a variety of mechanisms.

"They’ve shown their capability to do that or to engage in close quarter shooting attacks.

"That range of capability causes us significant concerns."

Police estimate that there are 200 "active" dissident republicans attached to three different groups and that some of their leaders have "significant terrorist experience".

Co-operation between police on either side of the Irish border and MI5 has been effective but they need more help from the public.

Mr Kerr said: "It’s a short-term fix to a security problem.

"The long term solution to paramilitary activity in Northern Ireland is with active community support and information.

"How we view intelligence in Northern Ireland is still framed by the past and by our troubled past.

"There’s no shared narrative.

"Therefore, both communities, both republican and loyalist, tend to see intelligence as a dirty word."

Sinn Fein leader Gerry Adams said there was no justification for dissident violence but understands some people's reluctance to come forward with information.

He said: "People from the broad Unionist and particularly the broad Nationalist section know how intelligence services ran agents, had counter gangs, colluded with paramilitaries and so on.

"Now, it’s gone past the time for any of these attacks.

"There’s now a peaceful and democratic way to pursue Irish unity and if these folks are at all serious about that, they’re not going to do it by trying to kill prison officers or PSNI officers."