UK terror threat level raised to severe, Brits told attack is 'highly likely'

The UK's terror level threat is to be upgraded to 'severe' in the wake of the deadly attack in Vienna. Home Secretary Priti Patel announced the change in a tweet, as she warned people to stay vigilant.

The alert level means an attack is 'highly likely.'

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"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," she tweeted.

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The step was taken as a precaution and was not based on a specific plot against Britain, Patel said on Twitter. Deadly incidents in France and Austria in recent weeks prompted the move, police said.

Last week, three others died in a knife attack in Nice, France, and a teacher was murdered in the French capital Paris last month.

Assessments of terror threat levels are taken by the Joint Terrorism Analysis Centre (JTAC), part of the MI5 intelligence service, which makes its recommendations independently from the government. They range between five categories of low, moderate, substantial, severe and critical.

The UK's terrorism threat level was raised to the highest rating, "critical", in the days following the Manchester Arena bombing in May 2017. The threat level remained at the second-highest rating, "severe", until last November last year when it was downgraded to "substantial", where it has stayed until now.

(With inputs from agencies)