Security chiefs in the Republic have drawn up two plans for the forthcoming visits of the Queen and US President Barack Obama — one dealing with dissident republicans and the other for Islamic extremists.
The strategies are part of an overall security plan, involving up to 6,000 gardai and troops drawn from across the Republic.
Separate intelligence-gathering and surveillance operations have been prepared within the plan as the sources of the main threats vary for the visits.
One senior anti-terrorist officer told the Irish Independent last night: "Obviously, the homegrown dissident groups will provide the main threat to the Queen's itinerary.
"On the other hand, we are closely monitoring the movements here of known sympathisers of international terrorist organisations, some with links to the al-Qa'ida network, from where any danger to President Obama is likely to emerge."
Special Branch officers have been ordered to step up surveillance on members of the three main dissident groups active on this side of the Border, the self-styled Oglaigh na hEireann -- which is regarded as being the most dangerous of the trio -- the Real IRA and the Continuity IRA.
PSNI detectives are also keeping a close watch on suspected activists from the "freelance" group of former Provisionals based in east Tyrone.
Earlier this month, the Irish Independent revealed that the freelance gang was responsible for the murder of the young Catholic PSNI constable, Ronan Kerr. Last night, the group claimed responsibility.
In their first public statement, the ex-Provisionals pledged to continue their murder campaign until "British occupation" had ended and Irish unity was achieved.
The group is centred around a core of former IRA activists, who have been joined by a small band of younger recruits from east Tyrone.
Since late last year, they have been considering joining the Oglaigh terror gang but still remain as "freelancers".
In their statement, they said they were responsible for "the recent execution of the RUC member in Omagh".
They also claimed that they had been responsible for the murder of two British soldiers at Massereene military barracks -- which was claimed at the time by the Real IRA -- the under-car bomb which seriously injured PSNI officer Peadar Heffron and the attack on the Policing Board headquarters in Belfast.
Last night, the PSNI said a man suspected in the killing of Ronan Kerr has been charged with terrorism offences.
The 33-year-old suspect was not named but he is accused of possession of firearms and explosives with the intent to endanger life and also charged with possession of articles likely to be of use in terrorism.
The suspect is the first man to be charged in relation to the murder; two other men were arrested and later released.