DUBLIN (AP) — A booby-trap bomb has exploded outside the home of a Northern Ireland policeman, injuring nobody but underscoring the continued threat from Irish Republican Army splinter groups.

The Police Service of Northern Ireland says Wednesday's failed attack involved a bomb attached to the underside of the policeman's private car in Londonderry, the second-largest city in Northern Ireland. It apparently dropped harmlessly from the car to the driveway as the officer drove off to work. It exploded hours later as bomb disposal technicians attempted to dismantle it using a remote-controlled robot.

The outlawed IRA designed under-car bombs in the 1980s to target off-duty officers and soldiers.