The new IRA group claimed responsibility for a bomb attack in which a prison officer was seriously injured due to a bomb exploding under his van, on Friday.
The new IRA is a group of one of a number of small militant groups opposed to a 1998 peace deal that largely ended three decades of violence in Northern Ireland between Protestants, who want to remain under British rule, and Catholics favouring unification with Ireland.
The group said in a statement to the BBC that it targeted the prison officer because he was responsible for the training of prison officers who work in a wing of the top security Maghaberry Prison in Co Antrim where there is a dispute between dissident inmates and the authorities.
Three men and a woman related to the case were arrested on Sunday and remained in custody on Monday, police said.
The new IRA was responsible for the 2012 murder of another prison officer, David Black, who was shot dead as he drove to work at the prison.
In the statement the dissident group said there would be more attacks on prison officers and "all aspects of the security forces".
Police said there was a "severe" threat to security forces as the centenary approaches of the 1916 anti-British Easter Rising.
In another incident on Sunday, an amount of bomb-making components and explosives were found buried in plastic barrels in the country park around 40 km(25 miles) north of Belfast in Northern Ireland.
"A number of small plastic barrels had been buried in a wooded area. Inside the barrels was a significant amount of bomb-making components including partially constructed devices and a small quantity of explosives," the Police Service of Northern Ireland said.
The haul was discovered after a member of the public reported a suspicious object on Saturday.
Detective Chief Inspector said it is too early to link the case to any particular group, but they are following a number of lines of inquiry.