A militant organisation based in West Belfast has claimed responsibility for recent letter bombs sent to buildings in London and the University of Glasgow. British police have reported the group claimed to be operating on behalf of the IRA.
The incident comes as the Brexit debate on the Irish backstop has fuelled calls for Irish reunification.
Last month Sinn Féin said a no-deal Brexit would inevitably lead to a vote on the independence of Northern Ireland from the UK and the reunification of Ireland.
“In the event, there is a no-deal Brexit then the Irish question looms very large because if that happens there will be an absolute imperative, a democratic imperative, to put the issue of Irish unity to the people by way of referendum,” Mary Lou McDonald, the Sinn Féin leader said.
“It would be an irresistible democratic necessity and so we have said to Jeremy today, just as we have said to Mrs May, and to the Taoiseach [Prime Minister of Ireland] and others, that there is a need now to begin planning, diplomatically politically, so that every contingency is considered including in the event of crash to trigger, as per the Good Friday agreement, a referendum.”
The group claiming responsibility for the letter bombs calls itself the IRA and is made up of militants opposed to Northern Ireland's 1998 peace deal. It is believed to be an offshoot of the Provisional IRA that was active during The Trouble, which saw 3,600 people killed before a peace agreement was reached.
The group, dubbed the 'New IRA', had split from the IRA due to a rejection of the 1997 ceasefire and subsequent 1998 Good Friday Agreement, and continues to seek the reunification of Ireland. In 2012 the original IRA had merged with several other smaller Republican militant groups.
The New IRA has been linked to recent incidents over the years including in 2014 when the group sent seven letter bombs to British Army recruitment offices in South-East England. This was the first Republican attack on the mainland UK since 2001. They are also suspected to be responsible for a car bombing attack on a courthouse in Derry earlier this year in January and in 2016 they were blamed for an attack in Belfast which left two injured and one dead.
The British intelligence service, MI5, and the Police Service of Northern Ireland (PSNI) report that the group is likely to be small and focused, with a core of no more than a few hundred people. MI5 said a severe threat persisted due to this group but stressed the people of Northern Ireland can continue with their lives relatively unaffected.