Germany declared all of Spain a coronavirus risk area on Friday after Spanish COVID-19 infection rates more than doubled in a week as the Delta variant spread rapidly among unvaccinated young adults.
The move, which includes the Balearic and Canary islands and takes effect on Sunday, will have a small immediate impact on travellers as it merely means they have to provide a negative test to avoid quarantine.
However, a further rise in Spain's infection rate could lead to mandatory quarantine for unvaccinated travellers, causing uncertainty ahead of the peak school summer holiday season, when Germans flock to beach destinations abroad.
Highly dependent on tourism, Spain is trying to strike a balance between opening up enough to entice back travellers while keeping infections in check to avoid putting off potential visitors.
Spanish travel associations said the measure would further damage the already struggling sector.
"It's ridiculous the lack of coordination between EU member states on travel recommendations," said Juan Molas, head of the Mesa del Turismo association.
Mallorca's FEHM hotel federation, whose members rely heavily on German travellers, said the move was far from trivial.
"It serves as a clear disincentive for tourists, further complicating the fragility of this season," the group said.
Tourism Minister Reyes Maroto said Spain was a safe destination for tourists, citing its vaccination programme and hospitalised patient numbers being kept under control.
She spoke after a report that Germany planned to add Spain to its risk list and after French Junior European Affairs Minister Clement Beaune advised French people to avoid Spain and Portugal for their summer holidays.
Germany's foreign ministry said it was also designating Cyprus as a high incidence area, meaning that incoming travellers must quarantine - which can be shortened if they test negative five days after entering the country.