Explosive devices sent to London transport hubs

Counter terror police in the United Kingdom are investigating after three packages containing improvised explosive devices were sent to separate London transport hubs.

The devices, believed to originate from Ireland, were discovered at Waterloo rail station, London City Airport's headquarters and Heathrow Airport on Tuesday.

Irish stamps were used on all three envelopes and two had return addresses in Ireland, according to Irish state broadcaster RTE. Irish police are assisting London's Metropolitan Police with the investigation.

The Met's headquarters Scotland Yard circulated images of two of the packages to sorting offices and transport workers in the capital, telling staff to "be vigilant and report suspicious packages to police".

Scotland Yard confirmed the device sent to the Compass Centre near Heathrow Airport was opened by staff, causing the device to initiate. This resulted in part of the package burning, it said in a statement.

The images showed the remains of the package sent to Heathrow and the envelope for the explosive device which was sent to Waterloo. Both have stamps featuring red hearts that are believed to originate from Ireland. 

Scotland Yard said it was working, "to ensure the safety of the public and staff working at transport hubs and mail sorting offices".

A spokesman said the incidents are being treated as linked, but there was an "open mind" regarding motives. All the packages were A4-sized white postal bags containing yellow Jiffy bags and appeared capable of igniting a small fire when opened, the Met police said.

An Irish security source told the Guardian: "violent dissident republicans" were the most likely source of the explosive devices, pointing to previous letter bomb attacks on targets in Britain and Northern Ireland in 2013 and 2014.

Tensions between the UK and Ireland have been mounting as the border in Northern Ireland becomes a bargaining chip in Brexit talks.

"The so-called dissidents have tried this before when they sent letter bombs that included army recruit centers in England and political figures. They have failed to mount an actual attack in England since 2001 and these are 'cheap' ways of causing terror across the Irish Sea," the source added.

The mayor of London, Sadiq Khan, said an investigation had been launched. "The police are treating the incidents as linked, but are keeping an open mind regarding the motives," he said. Khan confirmed there were no injuries and urged the public to report any suspect packages to the police.