Germany has announced mandatory tests for travellers returning from high-risk regions after new coronavirus cases breached the 1,000-a-day threshold for the first time since May, fuelling fears of a return to an economically disruptive lockdown.

After the Robert Koch Institute, Germany's public health agency, reported 1,045 new cases in a single day, health minister Jens Spahn said on Thursday that free compulsory testing will be in force from Saturday.

Part of the increase was due to more tests taking place, he said, but the impact of holidaymakers returning to Germany and of faltering social distancing discipline was also significant.

Germany classifies most of the world outside the European Union as high risk as well as some EU regions. These include Aragon, Catalonia and Navarre, and Belgium's Antwerp province.

The compulsory tests mean travellers will not have to quarantine for two weeks. Anyone who refuses to take the test could face a fine of up to 25,000 euros. "If anybody thinks they can be stubborn at the airport and deal with the fine when it comes later, no. They're going into quarantine for two weeks," Spahn stressed.

The minister said that he thought a renewed closure of shops could probably still be avoided, the head of the German doctors' union having observed earlier this week that Germany was already contending with a second wave of the coronavirus and risked squandering its early success by flouting social distancing rules.