Chancellor Angela Merkel's government has ordered people not leave their homes unless they have an exceptional reason such as grocery shopping, exercise or medical appointments.
Gatherings of more than two people are banned and a distance of at least 1.5 metres must be kept from others at all times.
Local governments have the power to set fines for transgressors, with city officials in Berlin saying their fines would be as high as €500.
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Similar announcements have come from across Germany's 16 states.
Customers at a weekly market in Hamburg try to stand 1.5 metres apart. Photo: DPA
Hesse, home to finance hub Frankfurt, and North Rhine-Westphalia both promised penalties of up to €200 for people who gather in groups of more than two.
Bavaria, Germany's largest state, has been the worst affected by the coronavirus so far, with more than 20,000 cases.
There, people who stand less than 1.5 metres apart risk being fined €150.
Queues of people standing far apart have become a common sight outside German supermarkets and pharmacies, with many sticking down tape to mark where people should stand on the pavement. Security guards often stand near by to tell customers when they need to allow more space.
However, German police have also reported numerous violations of the rules.
There have also been more than 1,100 deaths.