Three dissident republican gangs are fighting a deadly battle for supremacy to be recognised as the top terrorist outfit.
Senior anti-terrorist officers in the PSNI and An Garda Siochana are on high alert as the groups step up their efforts to grab the headlines with bomb attacks.
They fear the latest surge in dissident violence, which they expect to increase further in the run-up to Christmas, will claim the lives of innocent people as the latest campaign involves the use of "proxy" bombs to target security personnel and commercial premises.
Officers on both sides of the border are concerned at the fallout from the three-cornered battle between the well-established Continuity IRA, the group which calls itself Oglaigh na hEireann, and the latest dissident alliance, the New IRA.
After the latest proxy bomb attack in Belfast's main commercial centre, PSNI Chief Constable Matt Baggott said: "These groupings are trying to bring themselves to notice again.
"They seem to be in some form of bizarre competition to make sure they have a profile. We have seen letter bombs, under-car booby traps, blast bombs and hijackings," he said.
Mr Baggott said the surge in dissident activity would result in extra police patrols but said there would be no going back to the past and no "ring of steel" that had existed in Northern Ireland during the Troubles.
Gardai have stepped up surveillance on key suspects in the Republic where the dissidents have been attempting to establish logistical support for their bombing units in Northern Ireland.
A recent intervention by armed officers in the Republic resulted in the seizure of a large load of explosive mixture that was destined for use in a bomb attack across the border.
And last week a man was jailed by the Special Criminal Court in Dublin for possession of mortar launch tubes that were to have been used by the Real IRA.
The re-emergence of proxy bombs -- last used by the Provisional IRA -- has heightened tensions on the streets of Belfast and Londonderry.
Last week a bus driver was ordered to drive to a police station in Derry with a bomb on board.
On Saturday night a van driver was threatened by two masked men and told to deliver a package to the same barracks.
Parcel bombs addressed to senior police commanders and Northern Ireland Secretary Theresa Villiers were recently intercepted.
In the latest attack, a bomb containing 59kg of home-made explosive in a beer keg was left in a car outside a shopping centre at Victoria Square in Belfast city centre on Sunday night.
It was about a quarter the size of the Omagh bomb. The detonator exploded but failed to trigger the bomb.
The bomb was placed in the back of a silver Renault Laguna after the driver of the car had been stopped in the Ardoyne area by three masked men and ordered to bring the vehicle to the car park to be loaded with the bomb.
After abandoning the car, he ran to the nearby Musgrave Street police station and raised the alarm.
Hundreds of people were evacuated from restaurants and a cinema as British Army bomb disposal experts moved in. The detonator exploded as they were about to examine the car.
The alert caused massive traffic disruption in the city centre with several surrounding streets also sealed off.
A former policeman and his 12-year-old daughter escaped injury after he thwarted a booby trap bomb attack on his vehicle at his home in Dundonald near Belfast.
Ms Villiers and Stormont justice minister David Ford are among those who condemned the Victoria Square attack.
Ms Villiers said: "This was a reckless and callous attack on the people of Belfast which could have put many lives at risk.
"Families have been forced out of their homes and commuters delayed in their journey to work by this attempt to attack ordinary people going about their daily business."
Justice minister David Ford said the perpetrators had shown a total disregard for human life.
"The people responsible for this attack have nothing to offer and it is time they realised that Northern Ireland has moved on from the dark days of our past," he said.
Anne Connolly, chair of the Policing Board which scrutinises the police, said: "The use of the 'proxy bomb' tactic in recent days is concerning and further evidences the complete lack of care these people have for those who might get caught up in an attack."
Sinn Fein MLA Alex Maskey said almost 20 years after the first paramilitary ceasefires these groups still have not realised that there is no community support for their actions.
"The vast majority of society has endorsed the peace process and want to move forward," he said.
"There is now a democratic and peaceful way to bring about Irish unity. There is no reason whatever for any group to engage in or promote or support violent actions."
Stormont First Minister Peter Robinson said: "We are working together, trying to make progress, keeping Northern Ireland moving forward.
"There are still some people out there who would seek to drag us back, they won't be successful."
Deputy First Minister Martin McGuinness condemned those responsible and told the BBC they did not have the right to engage in that kind of behaviour.
The Republic's Deputy Prime Minister Eamon Gilmore also condemned the incident.
"It is nothing short of attempted murder, and comes in the wake of a number of recent incidents, all of which have been perpetrated by people who are without any political support and who have a reckless disregard for human life," Mr Gilmore said.
"A serious incident such as this, as we move into the Christmas shopping period, is an attempt to harm trade, tourism and employment in Belfast. I urge anyone with information to pass it directly on to the PSNI."