Germany partially closed its borders with the Czech Republic and Austria's Tyrol on Sunday over a troubling surge in coronavirus mutations.
A thousand police officers have been mobilised to ensure strict border checks, which recall the early days of the pandemic when EU countries hastily closed their frontiers.
What are the rules?
Under the new rules, only Germans or non-German residents are allowed to enter Germany.
Anyone who enters must provide a recent negative coronavirus test which is less than 72 hours old. The evidence of the test must be in either German or English.
Anyone entering Germany – including citizens and residents – must fill out the following form.
The rules are in place until February 21st, but are expected to be extended until at least the start of March.
Are there any exceptions?
Some exceptions to the rules exist allowed.
Cross-border workers and essential workers in ‘systemically relevant’ sectors, i.e. health and transport, are allowed to enter.
All workers will need to provide evidence of an employment contract.
They will however need to provide evidence of a negative coronavirus test.
There are also some exceptions for urgent humanitarian reasons.
People transiting through Germany will also be allowed to enter and will not have to provide evidence of a test.
The rules do not apply to the Austrian regions of Jungholz in Tyrol and the Kleinwalsertal municipality Mittelberg in Vorarlberg
How are the border controls being enforced?
German rail company Deutsche Bahn has suspended services to and from the affected areas.
At Frankfurt airport, the country's largest, federal police were on Sunday checking passengers arriving from Vienna and Prague.
Why are the borders being closed?
The restrictions are aimed at slowing the spread of new, more contagious variants that first emerged in Britain and South Africa, and have created new virus hotspots along the Czech border and in Austria's Tyrol region.
In addition to concerns over the coronavirus mutation, each Austrian state is currently above the threshold of 50 cases per 100,000 residents.
Chancellor Angela Merkel's government recently decided to extend Germany's partial lockdown until March 7 because of the risks posed by the variants, even if daily infection numbers have fallen over the past weeks.