DISSIDENT republican group the New IRA are reportedly the chief suspects behind three firebombs that were mailed to Heathrow, City Airport and Waterloo Station in London.
Gardaí last night confirmed they were assisting Metropolitan Police Counter Terrorism Command in their efforts to identify those responsible for the devices.
Security chiefs suspect the packages – sent from Dublin with An Post stamps – were intended to cause "mayhem" ahead of Brexit and the possibility of a hard Irish border, according to The Mirror.
A source told the paper: "The New IRA are the prime suspects and their inner core is very tight. It is thought they are using the skills of older experienced people to create mayhem.
"People believe this is a wake-up call, a warning to show what they could do, the disruption they can cause if the British abandon the backstop.
"It's about calling on those in power to take notice that the majority of people in Northern Ireland voted to remain in the EU."
The three "unsophisticated" IEDs were sent in A4-sized white postal bags containing yellow Jiffy bags and were capable of igniting a small fire when opened.
The first parcel to be discovered ignited at a Heathrow Airport outbuilding yesterday morning, but no one was injured.
The other packages later arrived to a post room at Waterloo – the UK's busiest railway station in central London – and an admin building at City Airport in east London, but were not opened and did not ignite.
All three letterbombs were mailed using stamps issued by An Post for Valentine's Day 2018 featuring red love-hearts and the words "Love Éire".
The packages also had Dublin return addresses, with one reading "Bus Éireann, Dublin".
Another source told The Mirror: "At least one of the packages originated from Dublin and it is believed that all of these packages are from Ireland.
"It is most likely to be a New IRA dissident republican-orientated attack but it could also be Islamic – there is nothing in the packages that could lead anyone to believe in specifics.
"There will now be a full investigation here in Ireland as well as in the UK to determine who it came from."
The New IRA is a paramilitary group active in Belfast and Dublin made up of dissidents who reject the Good Friday Agreement and the peace process.
Garda intelligence has been indicating for several months that the New IRA was preparing to ramp up its activities in 2019 and hoping to use the ongoing Brexit uncertainty to their advantage, reports the Irish Herald.
The well-quipped group already carried out a car bomb attack outside a courthouse in Derry back in January and is well-equipped with AKM assault rifles, sub-machine guns, handguns and large quantities of explosive Semtex.
Last month, Gardaí discovered an arms dump in a wooded area outside Omeath, Co. Louth, on the Cooley peninsula – including two rifles and around a quarter kilogram of Semtex, enough to act as a booster for three under-car bombs.
Authorities have issued advice to transport hubs across London to be vigilant.
The @metpoliceuk Counter Terrorism Command has launched an investigation after three suspicious packages were found at locations in London.
Our thanks go to police, security, transport staff and all involved for their swift actions to keep our city safe.https://t.co/Ow7xxILfRs
— Sadiq Khan (@SadiqKhan) 5 March 2019