Holidaymakers have been told to be vigilant if they are going abroad this summer over fears surrounding a planned mass tourism protests planned by anarchists.
Leftist Basques, a separatists group based in northern Spain, are planning an anti-tourism demonstration in San Sebastian to coincide with a week-long festival celebrating Basque culture.
Meanwhile, Spanish anarchists have begun targeting tourists who accuse them of "destroying" Barcelona and the Balearic islands such as Mallorca, according to reports in The Times.
Masked men ambushed an open-top bus containing British tourists near to the Nou Camp football stadium. A slogan "tourism is killing neighbourhoods" was then daubed on the bus before the tyres were slashed.
The attack was claimed by the Arran Jovent, a leftist youth movement with links to the anti-capitalist and pro-Catalina independence movement Popular Unity Candidacy (CUP).
The group have also shared several anti-tourism videos and messages on their social media pages, including a #touristsgohome hashtag on twitter.
A spokesperson for Arran told the BBC the protests were "not vandalism, but self-defence".
The spokesperson added: "Having to sign poor work contracts - that's violence - as is having to leave your neighbourhood and your support networks, because of tourism."
There has recently been reports of an exodus of locals living in tourists hot spots, such as Barcelona's Gothic Quarter, overwhelmed by the number of visitors. There was also a mass demonstration in Venice following fears the sheer number of visitors every year are beginning to take their toll on the ancient city.
Travel operators said that there could be further anti-tourism protests could across Europe..
Noel Josephides, chairman of Abta, the tour operators' association, said: "These protests are a wake-up call. It is a great shame but we will see more of them. They are adopting dangerous tactics and that shouldn't be happening.
"But the reason it is happening is because the local governments haven't been listening or taking the overcrowding seriously. The advice to tourists is use your common sense. Be vigilant and don't go where there might be a risk."
A Foreign Office spokesperson said: "We are aware of the protests and monitoring the situation. We are also in contact with the local authorities. There is no specific update to our travel guidance at the moment but we keep it under constant review."