An explosive device sent to Glasgow University has been linked similar packages sent to British Army recruitment centres in 2014.

Detectives want to hear from postal workers who may have come into contact with the devices, sent via post to major transport hubs in London as well as to the university between March 1 and March 22, Scotland Yard said.

A group claiming to represent the 'New IRA' claimed responsibility for the devices on March 11.

Further analysis of the five packages has now formally linked the packages to those sent to several recruitment centres five years ago.

Officers from the Met Police in London are leading the investigation into the devices.

On March 5, three packages containing small explosive devices were delivered to transport hubs in London.

The following day, a fourth package was recovered at Glasgow University.

Then on March 22, a fifth package was recovered, having been returned to a postal depot in Limerick, Republic of Ireland.

This package has since been forensically examined and is being treated as part of the same series.

No arrests have been made at this stage.

Deputy Assistant Commissioner Dean Haydon, senior national coordinator for the UK's Counter Terrorism Policing, said: "We are looking to identify any postal workers who may remember handling any of the packages between March 1 and 22.

"We have recovered forensic evidence following examination of the devices.

"You may have information that could help us with our investigation and it would also help with our forensic enquiries to be able to eliminate anyone who may have innocently come into contact with any of the five parcels after they were posted.

"Our enquiries continue, but clearly a key element of the investigation now is the link between the devices previously sent in 2014, and the five sent earlier this year. As with any investigation, we will be led by the evidence, but at this stage, our principal line of enquiry is that the devices were sent by a violent dissident republican group.

"The devices that were sent not only put their intended recipients in danger, but also endangered the lives of all those who handled and processed the parcels both in the Republic of Ireland as well as the UK.

"This was an extremely dangerous and reckless act and I would urge anyone who may have information about those responsible to contact police."