Dissident republicans pose a serious threat to society, Deputy First Minister Martin McGuinness has warned.
Speaking at the British-Irish Council meeting in Dublin, Mr McGuinness referred to the murder in Co Donegal of Tyrone man Andrew Burns (27), saying the killers had "no regard for the community, government or law and order".
"We face a real threat from the activities of some people within our society," he said. The Burns murder was "a dastardly deed and absolutely despicable".
"That presents a real challenge to all of us. We have to give our wholehearted support to the gardaí and the PSNI. These people are criminals and are trying to damage our society in a way that is totally unacceptable to us as political leaders."
The Garda investigation of Tuesday night's murder on the Donegal side of the Border near Strabane is continuing. It is thought inquiries are ongoing into claims the murder victim was a former member of a small dissident group, possibly the self-styled Óglaigh na hÉireann.