A small bomb has been defused by army explosives experts outside Newry, Co Down.
Police confirmed that a device discovered close to a roundabout on the main Belfast to Dublin road was "viable".
The security alert caused major traffic disruption on one of the busiest days on Northern Ireland's roads.
Dissident republicans opposed to the peace process have been blamed for planting the bomb.
The Ulster Unionist MLA for Newry and Armagh Danny Kennedy claimed dissident republicans were deliberately trying to heighten sectarian tensions over Easter when republicans on all sides take part in rallies to commemorate the anniversary of the 1916 Easter Rising.
He said: "They are sinister and evil people intent in creating havoc on the entire community. I fear the small section of hate-filled republicans will continue to seek to destroy lives."