Northern Ireland authorities say letter bombs have been found at two postal sorting offices, weeks after similar packages were sent to army facilities in England.
The devices, found in Londonderry on Thursday and Lisburn yesterday, were addressed to prison officers, according to the BBC and other media.
Last month, envelopes containing gunpowder, fuses and other parts were sent to seven army recruiting centers. A media outlet later received a claim of responsibility on behalf of "the IRA."
Most IRA members renounced violence in 2005, but dissidents still seek to undermine Northern Ireland's peace settlement.
Northern Ireland's Protestant First Minister, Peter Robinson, and his Catholic deputy, Martin McGuinness, said the bombers "are opposed to the democratic will of the people and want to drag us back to the past.
