MI5 has raised the official threat level to Britain from Northern-Ireland related terrorism, home secretary Theresa May has announced.

The British security service increased the level from moderate to substantial - which is the third most serious category out of five and means a terrorist attack is seen as a “strong possibility”.

Ms May said the move “reflects the continuing threat from dissident republican activity”.

In a statement to the House of Commons, she said: “As a result of this change, we are working closely with the police and other relevant authorities to ensure appropriate security measures are in place.”

The threat level to the UK from international terrorism remains at severe - meaning an attack is “highly likely”. This has not been changed.

Ms May said the threat level to Northern Ireland from Northern Ireland-related terrorism is also unchanged at severe.

‘Remain vigilant’

She added: “The public should remain vigilant and report any suspicious activity to the police.”

The main focus of violent dissident republican activity continues to be in Northern Ireland, “where they have targeted the brave police and prison officers who serve their communities day in and day out”, Ms May said.

She added: “The reality is that they command little support. They do not represent the views or wishes of the vast majority of people, both in Northern Ireland and the Republic of Ireland, who decisively expressed their desire for peace in the 1998 Belfast Agreement and have been transforming Northern Ireland ever since.”

The home secretary added: “However, it is sensible, given their stated aims, that the public in Great Britain should also remain vigilant and report any suspicious activity to the police.

“But we should not be alarmed, and this should not affect how we go about our daily lives.”

Press Association