Police say they also must exercise caution when responding to suspected bombs or other reported crimes near Northern Ireland's meandering 300-mile (500-kilometer) border with the Republic of Ireland, where dissidents have greater freedom to operate and attempt roadside ambushes. Saturday's defused bomb was left barely 1,000 yards (meters) from the border.
Last month, two dissidents were convicted of the 2009 murder of a 48-year-old policeman who was shot through the back of the head as he sat in his patrol car. In April 2011, a 25-year-old policeman was killed when a booby-trap bomb detonated under his private car in his driveway.
Both of the dead officers were Catholics, a reflection of how the past decade of peacemaking has dramatically transformed the makeup of Northern Ireland's once-overwhelmingly Protestant police. Today's force is 30 percent Catholic.
Associated Press writer David Stringer in London contributed to this report.