France and Spain have both reported large daily rises in coronavirus cases amid fears that parts of Europe could be hit by a second wave later in the year.
The UK government is currently advising against all but essential travel to Spain , including the Balearic and Canary Islands where infection rates are lower than on the mainland, and anybody coming back from the country is having to quarantine for two weeks.
But France is on an exemption list of nations which are deemed safe for Britons to travel to - and no self-isolation is required for them on their return home.
France has reported 1,695 new COVID-19 infections over 24 hours. This is the highest daily increase since 30 May, when they were up by 1,828.
Meanwhile in Spain , 1,772 new coronavirus infections were announced on Wednesday.
It marked the biggest jump in cases since a national lockdown was lifted in June.
In Germany, a doctors' union said it was already contending with a second wave amid a disregard for social-distancing guidelines that risked squandering the nation's early success in containing the virus.
The French government's top scientific body said of the crisis in its country: "The situation is precarious. We could at any moment tip into a scenario that is less under control, like in Spain.
"It is highly likely that we will experience a second epidemic wave this autumn or winter."
French authorities have strengthened public hygiene rules, with cities such as Lille, Nice and Toulouse ordering people to wear masks in busy pedestrian streets.
The city hall in Paris is in talks with the government to come up with a list of neighbourhoods where a mask rule should be enforced.
City officials want it to include shopping streets, the banks of the River Seine and parks and gardens, Le Monde reported.
The resurgence in Spain has prompted some regions to impose fresh restrictions on movement, making masks obligatory at all times outside the home and closing nightclubs again due to links to outbreaks.
Navarra, Aragon and Catalonia have registered more than 120 cases per 100,000 inhabitants over a 14-day period.
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Health clinics are trying to screen and isolate new infections, which are taking place mostly among the young, who in Spain and countries across the world are often ignoring social distancing, and the middle-aged.
According to Johns Hopkins University in the US, France has had at least 30,297 coronavirus-related deaths and 228,576 cases, while in Spain there have been 28,499 coronavirus-related fatalities and 305,767 cases.