Assistant Chief Constable Drew Harris also revealed that the security services thwart a plot to kill every couple of weeks.
The targets are not just serving or former officers, but their families too. Just days ago, dissidents tried to murder a father and his 12-year-old daughter in east Belfast.
The booby-trap bomb, planted under a former police officer's car, was spotted just in time before the school run.
ACC Harris told UTV that the bomb attempt was "a reckless act."
"Very dangerous obviously in terms of the ex-officer, his family and the people living in that area."
When asked if the PSNI had gathered any intelligence suggesting that it was going to happen, he replied: "We gather intelligence constantly.
"If we had intelligence to act upon - that would have been acted upon in this case.
"But we are constantly putting out warnings in respect of what we think the dissidents are attack-planning and where their next actions are going to be and part of that has been general warnings about under vehicle IEDs.
"Overall, we know that we have prevented numerous attack-planning conspiracies. We have prevented them coming together.
"Unfortunately, police officers do seem to be targeted, identified and targeted on a frequent basis. And that would seem to be nearly every couple of weeks, we would have a report of that every couple of weeks indeed."
In the past few weeks, the terror groups have changed tack, with letter bombs, countless alerts and the murder of north Belfast man Kevin Kearney.
His body was found in a lake at Alexandra Park last month. He was shot dead while walking his dogs - with the alarm being raised when the animals returned home without him.
The latest security assessment is that there will be further incidents.
"I think they are trying to ratchet up their campaign and this may in some ways be connected to ongoing concerns there are around protests and parades and just an effort to ratchet up community concern, community tension.
"I think their policy, their outlook is one of de-stabilising Northern Ireland and this is part then of the manifestion of that."
Most active of the groups are the so-called New IRA, Óglaigh na hÉireann and the Continuity IRA. They are still recruiting and trying to build up their arsenal.
ACC Harris continued:"They are making efforts certainly to acquire firearms and explosives, and you can see that in terms of the attacks that have happened.
"But we have not seen any major shipments. We are not seeing any regular consignment, we are not seeing, if you like, a terrorist-type arsenal being built up."