The Red Hand Defenders, a cover name for the Ulster Defence Association and the Loyalist Volunteer Force, has claimed responsibility for a bomb planted outside the offices of Republican Sinn Fein on the Falls Road in west Belfast yesterday.
Bomb disposal experts defused the device, a lunchbox containing an explosive substance with an alarm clock attached.
The UDA had recently announced a ceasefire following a bitter internal feud that led to the expulsion of many of the organisation's members in west Belfast.
Republican Sinn Fein is the political wing of the Continuity IRA, which claimed responsibility for a bomb that was defused outside the office of Democratic Unionist MP Nigel Dodds last month.
A letter bomb was also sent to Ulster Unionist Party headquarters in east Belfast last week, though the CIRA did not claim responsibility for the device.