Police have arrested three people following the murder of a workman at a Territorial Army base in Derry yesterday.
Mr David Caldwell (51), a civilian construction worker and a father of four, died of his injuries after a booby-trapped lunch-box exploded in a temporary building on the site at 7.30 a.m. yesterday.
If, as police suspect, dissident republicans are to blame, then Mr Caldwell is the first victim of their campaign since the Omagh bombing in August, 1998. He was a Protestant and a former member of the Ulster Defence Regiment, which he left in the mid-80s.
Loyalist paramilitaries, who killed a Catholic teenager in Belfast last week, threatened that they would carry out a "military response" to the murder.
Condemnation has been widespread, with the Irish and British governments and all parties in the North echoing calls by Mr Caldwell's partner, Ms Mavis McFaul, for an end to violence. She said that she could never forgive those responsible.
The DUP claimed that the attack was evidence of the Belfast Agreement's failure to establish peace. Sinn Féin said that the murder achieved nothing.
The "Real IRA" and the Continuity IRA have stepped up attacks on police and soft targets this year in the aftermath of their bomb attacks on army bases in Co Derry and blasts in London.
A "spectacular" assassination by dissidents remains a key threat to the political process, which is already under strain from alleged Provisional IRA activity and unionist protests that the ceasefire has been breached.