London, Nov 4 : The UK has raised its terror threat level from "substantial" to "severe", meaning an attack is highly likely, following the recent stabbing and shooting incidents in France and Vienna. The decision to raise the threat level had been taken by the Joint Terrorism Analysis Centre (JTAC), part of MI5, the British Security Service, on Tuesday, reprts Xinhua news agency. Home Secretary Priti Patel described the move as a "precautionary measure", saying that it was "not based on any specific threat". "The public should continue to remain vigilant and report any suspicious activity to the police," she said. The move came after four people were killed in a shooting by a suspected terrorist in Austrian capital Vienna on Monday night. Last week, three people died after a knife attack in Nice, France, after a teacher was murdered in Paris last month. The terror threat level in the UK had been at "substantial" since last November. The "severe" level is the second-highest level, with only "critical" above it, which was reached in May 2017 after the Manchester Arena bombing, in which 22 people, including a number of children, were killed and hundreds injured. The attack happened when Salman Abedi detonated a bomb at the end of a concert by US pop singer Ariana Grande at Manchester Arena. It was the worst terror attack in the UK since the London bombings in 2005 in which 52 people died. /IANS