A dissident republican group calling itself the IRA has said it was responsible for the attempted murder of a prison officer in east Belfast.
The 52-year-old officer suffered serious injuries when a bomb exploded under his van on Friday morning.
The group, which is widely referred to as the new IRA, said he was targeted for training officers at Maghaberry Prison near Lisburn in County Antrim.
Three men, aged 34, 41 and 45, and a 34-year-old woman have been arrested.
Police said the device partially exploded when the prison officer, a father of three, drove over a speed ramp in Hillsborough Drive.
He is in a stable condition in hospital.
In a statement to the BBC, the group said he was one of a number of prison officers on a list of "potential targets".
They claimed he was targeted because he was responsible for training prison officers who work in a wing housing dissident republicans at Maghaberry prison.
A spokesman for the group said last week's attack was the result of an ongoing dispute between dissidents and the prison authorities about their treatment in the prison.
Police have not commented on the nature of the device used in the attack, but the group's statement claimed it contained a quantity of Semtex and a commercial detonator.
The same dissident organisation shot dead prison officer David Black as he drove to work at Maghaberry in November 2012.
After Friday's attack, the Police Service of Northern Ireland said it was deeply concerned that dissident republicans were determined to escalate their activities to mark the centenary of the 1916 Easter Rising.
Assistant Chief Constable Stephen Martin warned that further attacks in the run up to Easter were "highly likely".
There has been widespread condemnation of Friday's attack, including from Northern Ireland's First Minister Arlene Foster and Deputy First Minister Martin McGuinness.
The group widely referred to as the New IRA was formed in the summer of 2012, from the amalgamation of a number of dissident republican organisations.
It is the largest dissident group currently active.