The UK domestic security service, MI5, has increased the threat level from Northern Ireland to substantial, from its previous level of moderate, the BBC reports.
This means there is "a strong possibility" of a terror attack in Great Britain.
Home Secretary Theresa May has noted that the adjustment "reflects the continuing threat from dissident republican activity."
In March, the New IRA murdered a police officer. Last month the group claimed that it is "determined to take the war to the age-old enemy of our nation."