Updated 12.30
Security services in the North are on heightened alert as the threat level remains high that dissident republicans will carry out an attack in the lead up the centenary of the Easter Rising.
It is after a prison officer suffered serious injuries in a bomb blast on Friday and a number of viable devices were uncovered in Co Antrim over the course of this weekend.
The 52-year-old officer needed surgery after a device detonated under the van he was driving to work.
The BBC has said a group called the New IRA has claimed responsibility for the attack, in a statement made to them.
Northern Ireland Home Affairs Correspondent Vincent Kearney says the New IRA formed in 2012 and was responsible for the shooting dead of David Black while on his way to work in Maghaberry prison in 2012.
Members of the PSNI and other security forces have been told to remain on alert.
Alan Murray, Belfast-based Security Correspondent told Breakfast about his conversations with police in the North:
"Dissident Republicans are intent in upping their profile, carrying out more attacks by the time of the Easter Sunday parades.
They, and the Prison Officers Association has said they expect another attack will be imminent - and the attempt will be to kill a prison officer specifically.
But, they say a police officer, a soldier, anyone connected to the security services is under threat."
Meanwhile, four people are still being questioned after Friday's van attack.
Three men and one woman, aged in their 30s and 40s, were arrested last night.
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Assistant Chief Constable Stephen Martin appeals for information following the attempted murder of a Prisoner Officer this morning. We need your support. If you any information that can help, please call us on 101.
Posted by Police Service of Northern Ireland on Friday, 4 March 2016
On Friday, the PSNI warned that dissident Republicans are intent on killing security force members to mark the centenary of the Easter Rising in Dublin.
Yesterday, the PSNI discovered bomb-making parts in Co Antrim.
Meanwhile, a bomb was found in Derry overnight. More information on that as we get it.
A security alert near a primary school in Dunnmurry, Co Antrim has ended after the PSNI declare a device they examined to be a fake.
An Garda Síochána is equipped to deal with the threat the Commissioner is insisting.
Speaking at a passing out of new garda recruits from the force's training college at Templemore today, Nóirín O'Sullivan said all leave for gardaí in Dublin has been cancelled for the commemoration period to ensure that policing levels are sufficient to deal with security concerns:
"It shows that there is a very small, but very determined cohort of people, who are determined to cause harm to communities north and south of the border.
Obviously it is an ongoing live investigation in Northern Ireland and we are working very closely with our colleagues in the PSNI.
It is why the activities of dissident Republicans remain a top priority for An Garda Síochána."
