The UK is closely watching rises in COVID-19 cases in other European destinations such as France and Germany after issuing a 14-day quarantine on travelers from Spain at the height of the summer vacation season.

The imposition of a UK quarantine on Spain is one of the starkest indications to date that Europe could face a second wave of economic turmoil as governments scramble to head off a rise in cases from the Mediterranean to the North Sea.

Shares in airlines and travel companies - already struggling due to coronavirus lockdowns - tumbled while Spain pleaded for Britain to exclude the Balearic and Canary islands from the quarantine.

"We have to keep the situation under review and I think that is what the public would expect us to do," junior health minister Helen Whately told Sky News when asked about Germany and France possibly being next to face quarantines.

"If we see rates going up in a country where at the moment there is no need to quarantine, if we see the rates going up, we would have to take action because we cannot take the risk of coronavirus being spread again across the UK," she said.

On Sunday, Spain's foreign minister insisted the country is "safe" for holidaymakers in an attempt to reassure travelers from other European nations. 

Four days prior to the UK's announcement, Norway imposed a 10-day quarantine ruling on travelers entering the country from Spain and the Spanish government is keen to ensure other countries don't follow suit and further damage its tourism industry.

Spain has suffered fresh outbreaks of COVID-19 with around 900 new cases announced on both Thursday and Friday but insists they are under control.

Foreign minister, Arancha Gonzalez Laya, said: "Spain is a safe country for tourists and for Spaniards, (but) like in any other European country, we are seeing outbreaks. The outbreaks in Spain are perfectly controlled. We have three that are the most important outbreaks at the moment in Barcelona, in Lleida, that in Zaragoza, all of them are perfectly traced."

Spain is also hoping that quarantine rules will be relaxed for tourists visiting the popular Balearic Islands, which Laya says have very few cases of the virus. She added: "In particular, our dialogue efforts at the moment are focused around excluding from the quarantine measures, the Balearic and the Canary Islands for two reasons.

"Number one, these are islands, very safe territories. Number two, their epidemiological data is extremely positive. Well below epidemiological data in the UK."

The quarantine requirement came into effect from midnight (2300 GMT on Saturday), making it almost impossible for travelers to avoid it by rushing home. The British foreign ministry also advised against all but essential travel to mainland Spain, a move likely to prompt tour operators to cancel package holidays and trigger claims against insurers.

The move has angered holidaymakers who are already in Spain and will now be forced to quarantine, as well as those who were preparing to head to the country for a summer break, but UK foreign minister Dominic Raab says the action was necessary.

"We can't make apologies for doing so," he said to Sky News. "We must be able to take swift, decisive action, particularly in relation to localized (outbreaks), or internationally in relation to Spain or a particular country, where we see we must take action." 

Britain's opposition Labour Party said the news was "deeply concerning" and called for support for British people affected.

Spain had been on a list of countries that the British government had said were safe for travelers to visit – meaning tourists returning home would not have to go into quarantine. The announcement of such lists just weeks ago had allowed Europe's tourism sector a chance for revival after the near-total shutdown prompted by the COVID-19 pandemic.

Read more: The New Normal: Tourism

But the abrupt travel restriction announced by Britain will have a far greater impact on Spain's tourism industry. According to the National Institute of Statistics, a total of 18 million Britons visited Spain in 2019, the largest group by nationality and accounted for more than 20 percent of the country's foreign visitors. Tourism normally accounts for 12 percent of Spain's economy.

Antonio Perez, the mayor of Benidorm, a resort on Spain's Costa Blanca that is hugely dependent on British tourists, called the move "another tough blow."

"We have suffered a lot this year and then this happened. We thought that the British were going to come back but this makes things harder for now," he said.

And the British move will affect not just Spain's tourism sector but airlines and travel companies struggling to get back to business.

Europe's biggest travel company TUI said it was cancelling all departures on Sunday to Spain from the United Kingdom, and was urgently reviewing future flights.

"We're incredibly disappointed that we didn't get more notice of this announcement, or that this decision wasn't made yesterday, as many Brits travel on holiday at the weekend," said TUI's UK managing director Andrew Flintham.

Read more: France gears up for second wave after surge in new cases

EasyJet and British Airways said they did not plan to cancel flights over the coming days.

Spain is one of the worst hit countries in Europe by the pandemic, with more than 290,000 cases and over 28,000 deaths. It imposed very strict lockdown measures to contain the spread, gradually easing them earlier this summer. But the last few weeks have brought a surge of cases, forcing local lockdowns to be reimposed in some areas.

The Catalonia region reported 1,493 new coronavirus cases and three deaths on Saturday. The regional government has urged residents of Barcelona to stay at home, and ordered all discos to shut from Saturday for the next 15 days.

Britain itself has been the worst hit country in Europe by the pandemic, with more than 328,000 cases and an official death toll of more than 45,600.