The terror threat level in Northern Ireland has been raised from “substantial” to “severe”.

Chris Heaton-Harris, the Secretary of State for Northern Ireland, announced MI5 made the decision on Tuesday.

The escalation means an attack is highly likely, with Mr Heaton-harris saying in a statement the threat is “constantly monitored and is subject to a regular formal review”.

The levels are designed to give an indication of how severe the terror threat is in the country, with five rankings from low to critical.

The Northern Ireland secretary said that the public “should remain vigilant, but not be alarmed”.

He encouraged people to “continue to report any concerns they have to the Police Service of Northern Ireland”.

'An increase in levels of activity'

The raised level follows “an increase in levels of activity relating to Northern Ireland Related Terrorism, which has targeted police officers serving their communities and also put at risk the lives of children and other members of the public”, Mr Heaton-Harris said.

He added: “These attacks have no support, as demonstrated by the reaction to the abhorrent attempted murder of DCI Caldwell.

“I pay tribute to the tremendous efforts of the Police Service of Northern Ireland and security partners, and the determination and resilience of the Northern Ireland people, who are making Northern Ireland a safer place to live and work.

“The political future of Northern Ireland rests with the democratic will of the people and not the violent actions of the few. Together we will ensure there is no return to the violence of the past.”

John Caldwell, a Detective Chief Inspector in Omagh, was shot multiple times by two gunmen in front of his 12-year-old son in February.

DCI Caldwell, 48, was putting footballs in the boot of his car following a youth training session for the team Beragh Swifts, who he coached.

Two men were arrested in connection with the shooting in February, but later released.

DCI Caldwell remains in hospital in a critical condition.

Police Service of Northern Ireland (PSNI) Chief Constable Simon Byrne said: "This is part of an ongoing process of monitoring the threat level in Northern Ireland, which is conducted by MI5.

"We have spoken publicly about the number of attacks that have taken place in recent months, not least the attempted murder of DCI John Caldwell on February 22.

"We will relentlessly pursue those who seek to cause harm and terrorise our communities, and attack my officers and staff, and I pay tribute to them as they continue to deliver for our communities."

This is a breaking news story. Follow for more updates.