France has warned its citizens against travelling to Spain and Portugal because of a surge in cases caused by the fast-spreading Delta variant.
The French government allows people to travel to all EU members as long as they are fully vaccinated and show a negative test on their return.
The bloc’s digital Covid certificate also allows EU citizens to travel freely across borders but members still retain the right to deny entry from certain countries.
France's Europe Minister Clement Beaune advised travellers to avoid crossing into Spain and Portugal.
"For those who have not yet booked their holidays, avoid Spain and Portugal as a destination," he said.
"It's better to remain in France or go to other countries."
Mr Beaune said France, which fears being hit by a fourth wave of coronavirus infections this summer, was considering restricting travel in Europe because of the spread of the variant.
"We have to be careful ... the pandemic is not over," he said. "We will decide in the coming days, but we could put in place reinforced measures."
Germany has banned incoming travellers from Portugal, where the Delta variant is now dominant. Only German citizens or residents are allowed in from Portugal and they must quarantine for two weeks upon arrival.
France warns of virus surge
Mr Beaune said France was "closely following the situation in countries where the flare-up [in infections] is very fast”.
He singled out the Spanish region of Catalonia, where Barcelona is located, and "where many French people go to party and for holidays".
Portuguese Foreign Minister Augusto Santos Silva said the health situation in his country had "worsened" and concerns from France were "understandable”.
The Catalonia region this week reimposed curbs on nightlife to try to tame a surge in infections, especially among unvaccinated young people.
Nightclubs will be closed from this weekend and a negative Covid-19 test or proof of vaccination will be needed to take part in outdoor activities involving more than 500 people.
Last week, nearly half of Portugal's population was again placed under a night-time curfew after the number of daily new cases exceeded 2,000 for the first time since mid-February.
The clampdown came as the EU struck a deal with non-EU member Switzerland to recognise each other’s Covid certificates.
EU ambassador Markus Ederer said the bloc had proposed a similar arrangement with Russia.
"In that spirit, we have approached the Russian Ministry of Health and proposed discussing whether Russia would be interested in such a process," he said.
Kremlin spokesman Dmitry Peskov said a compromise could be reached.
The UK on Thursday scrapped mandatory isolation requirements for vaccinated travellers returning from amber countries.
The measures apply only to returning UK residents who have received both shots in England, Wales, Northern Ireland or Scotland.
However, the government plans to extend the approach to visitors from major holiday markets including the US and EU later this summer.
Britain recorded 32,548 positive Covid cases and 33 deaths in the latest 24-hour period.