A suspicious package found at an Irish postal depot appears to be identical to a series of devices sent to the UK, police in Ireland have said.
Army bomb disposal experts were called to the postal sorting office in Limerick on Friday morning after the package was discovered.
The Defence Forces later confirmed a "viable improvised explosive device" had been found contained in a plastic envelope.
Irish Justice Minister Charlie Flanagan said a stamp on the package found in the An Post depot on Dock Road in the city was similar to those sent to the UK earlier this month.
He added: "This is a despicable act.
"The sending of incendiary devices like this is totally unacceptable. I hope the people responsible are brought to justice."
A spokesman for the Defence Forces said: "A viable improvised explosive device contained in a plastic envelope was identified and made safe. The device was then handed over to An Garda Siochana for further investigation."
A group calling itself the IRA has claimed responsibility for parcel bombs sent to major transport hubs in London and the University of Glasgow.
The group said it posted five devices to addresses in Britain, however only four had been discovered at the time the claim of responsibility was sent to a Belfast newsroom.
Mr Flanagan said the item found in Limerick could be the fifth.
"We have reason to believe this could be the case," he said.
The packages that arrived at Waterloo railway station and offices at Heathrow and London City airports on March 5 and 6 were posted with Irish stamps and had Dublin as the return address, prompting Irish police to join the investigation.
The stamps appeared to be those issued by the Irish postal service for Valentine's Day 2018, featuring a heart motif and the words "Love Eire N".
All packages were A4-sized white postal bags containing yellow Jiffy bags and appeared capable of igniting a small fire when opened.
No-one was injured in any of the incidents in Britain.
On Friday, a Garda spokesman said: "This parcel appears to be identical to parcels - pending closer forensic and ballistic examination - discovered earlier this month in London and Glasgow.
"An Garda Siochana continue to liaise with the UK authorities in relation to these investigations."