A third man has been arrested by police probing the murder of a prison officer in Northern Ireland.
The suspect, 29, was detained in the Irish Republic by police. Earlier, two other men including prominent dissident republican Colin Duffy were arrested north of the border.
David Black, 52, was gunned down during a high speed ambush on Thursday on a motorway as he drove to work at Maghaberry high security prison. His killing has prompted condemnation from across Great Britain and Ireland and police have blamed it on dissident republicans.
A statement said: "Gardai have arrested a 29-year-old man in Co Leitrim this evening in connection with the murder of 52-year-old David Black in Co Armagh yesterday morning. The man is detained in Carrick-On-Shannon Garda Station under Section 30 Offences Against the State Act 1939."
Duffy was detained with a second man in Lurgan, Co Armagh, just miles from where Mr Black was ambushed on the M1 motorway on his way to work at the top security prison, near Lisburn, Co Antrim.
Duffy, 44, who has been cleared of murder charges on three separate previous occasions - the latest last January after two soldiers were shot dead outside Massereene Army barracks in March 2009 - was arrested at his home in the Kilwilkie estate where republicans opposed to the peace process have huge support.
Politicians on all sides condemned the murder of the prison officer, who was planning to retire next year after more than 30 years of service.
Taoiseach Enda Kenny, who was in Armagh for talks with Northern Ireland First Minister Peter Robinson and Deputy First Minister Martin McGuinness, said the dissident republicans had been linked to criminality and drug dealing which had also led to deaths on the streets of Dublin.
He said: "We do not want to see a return to this, nobody on this island wants to see a return to this."
Police have confirmed the dark blue Toyota Camry car used by the gunman and then later burned out had Dublin-registered number plates. Duffy and the second man, 31, are being held at Antrim, but detectives believe it will be up to the public to give them the breakthrough they need.