A group calling itself the IRA has claimed responsibility for parcel bombs sent to major transport hubs in Britain last week.
It also said one parcel, sent to a British army recruitment officer, may not have been discovered yet.
The group claims it posted five devices to addresses in Britain, however only four have been discovered.
The claim was received on Monday by Belfast-based newspaper The Irish News using a recognised codeword.
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”.
The senders’ addresses were given as Dublin, with two having adding coach operator Bus Eireann.
Police Scotland said a controlled explosion was carried out as a precaution on a suspicious package found in the mailroom at Glasgow University, after several buildings had been evacuated.
According to the Irish News: “(The group) claimed that three were sent to ‘commercial targets’ while the remaining two were posted to British army recruitment officers.
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“The group said a device discovered at Glasgow University was intended for a British army recruitment officer who works there.”
All 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 and no arrests have yet been made.
A spokesman from the Metropolitan Police said the force is aware of the claim, however investigations are ongoing.
“The Metropolitan Police and Police Scotland are aware of the claim of responsibility for the devices that were received at three buildings in London and at the University of Glasgow on March 5 and 6,” he said.
“The investigations into these devices continue and relevant inquiries are being made in relation to the claim that has been made.
“Given the packages received last week bore similarities to devices sent in the past which were linked to dissident groups associated with Northern Ireland-related terrorism, officers were already looking at this as a line of inquiry.
“However, we continue to keep an open mind and inquiries continue.
“We are also aware that those claiming responsibility have indicated five devices were sent.
“At this time, only four devices have been recovered.
“Extensive advice has already been issued to relevant businesses and sectors to be vigilant for and report suspicious packages to police. This advice was previously sent to armed forces personnel and is being reiterated again in light of this claim.”
“We continue to urge the public to remain vigilant and report anything suspicious to police.”