- MI5 raises Northern Ireland terrorism threat level to 'severe', meaning an attack is 'highly likely'.
- Decision follows attack on off-duty officer in February claimed by dissident republican group.
- Increase to second-highest threat level comes ahead of 25th anniversary of Good Friday Agreement.
- PSNI preparing to boost security, as Biden is expected to visit the region soon.
- UK Northern Ireland secretary urges public to remain vigilant but not alarmed.
Northern Ireland terrorism threat raised to second-highest level
Assessment by domestic intelligence agency MI5 means attack is ‘highly likely’
