A group calling itself the "IRA" has claimed responsibility for the explosive device sent to the University of Glasgow last week, Police Scotland confirm.
A joint statement from Police Scotland and the Metropolitan Police said the claim of "IRA" responsibility was received on Monday 11 March using a recognised codeword by a Belfast-based newspaper.
The Met and Police Scotland said similar packages were sent in the past by dissident Northern Ireland groups.
This comes after devices were received at three buildings in London and at the University of Glasgow on March 5 and 6. The packages that arrived at Waterloo railway station and offices at Heathrow and London City airports on Tuesday were posted with Irish stamps and had Dublin as the return address. No one was injured and many buildings across the West End campus of Glasgow University were evacuated. Both the London Metropolitan Police (Met) and Police Scotland are investigating and "relevant enquiries are being made".
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.
"The group said a device discovered at Glasgow University was intended for a British army recruitment officer who works there."
In a joint statement, Police Scotland and the Met said:
"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 enquiry. However, we continue to keep an open mind and enquiries continue.
"We are also aware that those claiming responsibility have indicated five devices were sent. At this time, only four devices have been recovered."
To read their full statement, click here.