The terrorism threat in the UK has been upgraded to severe in the aftermath of the terror attack in Vienna overnight and a string of violent incidents in France, the government has announced. The decision by the independent Joint Terrorism Analysis Centre (Jtac) means the terror risk is back at its second highest level, meaning that an attack is judged to be “highly likely” – where previously it was simply deemed “likely”. The home secretary, Priti Patel, said: “The British people should be alert but not alarmed. This is a precautionary measure following the horrific events of the last week in France and last night in Austria and is not based on a specific threat.” Jtac had unexpectedly lowered the national threat level to substantial last November, following the death of the Isis leader, Abu Bakr al-Baghdadi; prior to that it had been at severe or even higher since August 2014. Over the past few days, Islamist propagandists using social media have particularly focused on France, whose president, Emmanuel Macron, has robustly defended the country’s secularism, following a series of attacks that began last month when a teacher was killed after he had shown cartoons of the prophet Muhammad to pupils. But the tipping point appears to have been Monday night’s attack in the Austrian capital, where five people, including an attacker, died in a country not known for being targeted by Islamists. It is well established that terror attacks in one country encourage copy cats elsewhere. Intelligence agencies said earlier that the UK is expected to be “particularly vigilant” in the aftermath of the Vienna attack, particularly as England is poised to enter its own lockdownon Thursday. Intelligence sources added it was unclear, at this stage, if the attacks in Austria were timed to coincide with the night before the start of a lockdown, when more people than usual would have been out in the evening and on the streets. But it would be prudent to take into account that timing in the run-up to the start of the England-wide lockdown expected to begin at just after midnight, in the small hours of Thursday. Patel said: “As I’ve said before we face a real and serious threat in the UK from terrorism. I would ask the public to remain vigilant and to report any suspicious activity to the police.” Last month, MI5‘s new director general, Ken McCallum, said the security service had disrupted “27 late-stage terrorist attack plots in Great Britain” of which the majority were Islamist extremists. Jtac is based within MI5 but operates independently of it as well as ministers. Its membership is composed of all the intelligence agencies who take a view on the threat to the UK from all forms of terror.