Irish terror threat 'substantial'
The threat level to Great Britain from Irish-related terrorism has gone from moderate to substantial, meaning an attack is a "strong possibility", Home Secretary Theresa May said.
It is the first time that this threat level has been published, the Home Office said. The threat from international terrorism remains severe.
Mrs May said: "The director-general of the Security Service has informed me that he has raised the threat to Great Britain from Irish-related terrorism from moderate to substantial, meaning that an attack is a strong possibility."
"Judgments are based on a broad range of factors, including the intent and capabilities of terrorist groups," she added.
"This is the first time we have published the Irish-related threat assessment to Great Britain. This is in the interests of transparency and to encourage people to remain vigilant. The first and most important duty of government is the protection and security of the British people.
"We have been consistent in stating that the threat to the UK from terrorism is real and serious. The balance we aim to strike is keeping people alert but not alarmed. I would urge the public to report any suspicious activity to the police and security services in their continuing efforts to discover, track and disrupt terrorist activity."
A spokesman for the Police Federation in Northern Ireland said: "It confirms the predictions of the chairman, Terry Spence, that this threat would move beyond Northern Ireland. The chairman is on the record as having pointed out that the terrorist threat in Northern Ireland historically ends up going across to Great Britain to attack the political, economic and infrastructural targets there because of the political impact it can make."
A series of attacks on members of the security forces in Northern Ireland have failed in recent months. But two soldiers and a policeman have been shot dead and there have been attacks on police stations.
Northern Ireland First Minister Peter Robinson said dissident republicans had no widespread support.
He said: "The continued existence of such groups is in direct defiance of the wishes of the people of Northern Ireland who have expressed clearly their desire for peace and stability. It is a worrying sign that the intelligence services have upgraded the threat level, which underlines the need for adequate police resources to tackle this threat and stamp it out completely."