Gardaí have mounted a series of armed checkpoints across the north side of Dublin city following the shooting dead of Alan Ryan yesterday.
The 32-year-old, who was known to Gardaí for his links to the Real IRA, was shot dead as he lay injured on Grange Lodge Avenue shortly after 3.30pm yesterday afternoon.
Gardaí concerned about reprisals have placed armed checkpoints around the Donaghmeade area of the city.
Garda sources said Ryan had "a long list of enemies", and a large team of detectives are identifying those with the motive and capability for such for an attack.
Tensions are high in north Dublin and officers from the Special Detective Unit, which targets terror groups, joined local units in patrols and check points last night.
However, gardaí will also examine the possibility that associates within the RIRA could have carried out the attack.