A suspicious parcel found at a Irish postal sorting office appears identical to letter bombs sent to buildings in London and the University of Glasgow this month, Irish police say.
Police say they are investigating the parcel, which was identified at a sorting office in the county of Limerick early on Friday, and are liaising with British authorities.
The army's bomb disposal team was on the scene.
A dissident Irish nationalist group calling itself the "IRA" claimed responsibility for three letter bombs sent to buildings in London and a fourth to Glasgow.
The small group is made up of militants opposed to Northern Ireland's 1998 peace deal.
It is separate and far smaller than the Provisional IRA, which was responsible for almost half of the 3600 deaths during 30 years of violence and which disbanded after the peace deal.
British police said those claiming responsibility had indicated that five devices were sent and Irish Justice Minister Charlie Flanagan was quoted as saying the postage stamp on the Limerick parcel suggested it "could well be the fifth".
Australian Associated Press