The head of Germany's public health agency has said he is "very concerned" by rising infections in the country.
"We are in the middle of a rapidly developing pandemic," Lothar Wieler, head of the Robert Koch Institute (RKI), reports BBC.
Wieler said Germans had become "negligent" and urged people to wear masks and respect social distancing and hygiene rules.
In the past week, the country has recorded 3,611 new infections.
The warning comes as countries across Europe grapple with new infections and the problem of travellers moving across the continent for the summer holidays.
On Tuesday Germany issued a travel warning for three regions in Spain - Aragón, Catalonia and Navarra - which have seen a recent spike in infections.
It comes after the UK imposed a 14-day quarantine on all arrivals from Spain - a move Spanish Prime Minister Pedro Sánchez called "unjust".
Germany announced on Monday a programme of free, mandatory coronavirus testing for travellers returning from a list of high-risk countries. The list currently includes Brazil, Turkey and the US, and officials said it will be updated daily.