The threat level for a terror attack in the UK has been raised from substantial to "severe" for the first time since November.
People are being urged to "remain vigilant", but the home secretary, Priti Patel, said the move was precautionary and not based on any specific threat.
She said on Twitter the change had been made after assessment by experts at the UK's Joint Terrorism Analysis Centre (JTAC).
It follows an attack in the Austrian capital Vienna on Monday night when four people were killed.
Police in the country said the suspect was carrying an assault rifle and was also wearing an explosive vest.
Two men and one woman were among those killed, whilst 15 others were admitted to hospital.
Home secretary Priti Patel said on Twitter: “The Joint Terrorism Analysis Centre has changed the UK terror threat level from substantial to severe.
“This is a precautionary measure and is not based on any specific threat.
“The public should continue to remain vigilant and report any suspicious activity to the police.”
The "severe" level is the second-highest level, and means an "attack is highly likely", with only "critical" above it which means an attack is "highly likely in the near future".
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The threat level was last raised to critical after the Manchester Arena bombing in May 2017.
What are the five threat levels?
- Low - an attack is highly unlikely
- Moderate - an attack is possible but not likely
- Substantial - an attack is likely
- Severe - an attack is highly likely
- Critical - an attack is highly likely in the near future
