About two million people who have not been fully vaccinated against Covid-19 have been placed in lockdown in Austria as the country faces a surge in cases.
“We are not taking this step lightly, but unfortunately it is necessary,” Chancellor Alexander Schallenberg said.
Unvaccinated people will only be permitted to leave home for limited reasons, like working or buying food.
About 65% of Austria’s population is fully vaccinated – one of the lowest rates in Western Europe.
Meanwhile, the seven-day infection rate is more than 800 cases per 100,000 people, which is one of the highest in Europe.
Overall, Europe has again become the region most seriously affected by the pandemic and several countries are introducing restrictions and warning of rising cases.
However, the UK, which has one of the highest Covid infection rates, has yet to reintroduce restrictions, despite health leaders calling for rules like mandatory face coverings in crowded and enclosed spaces to be brought back to avoid a winter crisis.
The measures introduced in Austria on Monday, which come amid growing pressure on the nation’s hospitals, will initially last for 10 days.
Children under the age of 12 and people who have recently recovered from the virus will be exempt.
Over the weekend, hundreds of people protested outside the chancellery in the capital, Vienna, waving banners that read: “Our bodies, our freedom to decide.”
One female protester said she was demonstrating “to fight for my rights”. “It is totally discriminatory what is happening here,” she said.
But Prof Eva Schernhammer, of the Medical University of Vienna, said the measures were needed, warning that hospital intensive care units were filling up. “It’s already projected that within two weeks we’ll have reached the limit,” she said.
Unvaccinated people were already barred from visiting restaurants, hairdressers and cinemas, but will now be expected to stay at home.
“In reality we have told one-third of the population: you will not leave your [home] apart for certain reasons,” Mr Schallenberg said.
“That is a massive reduction in contacts between the vaccinated and the unvaccinated.”
The government says police will carry out spot checks in public spaces to determine the vaccination status of individuals, and issue fines to those caught breaking the rules.
There was a last-minute rush at vaccination centres in Upper Austria on the eve of the new restrictions.
But critics have questioned whether the move is constitutional. The far-right Freedom Party has said it will create a group of second-class citizens.