The holiday island of Sylt, just off the coast on the border of Germany and Denmark, is one destination not necessarily looking forward to the sudden attention.

With radical left-wing groups planning to set up a protest camp on the island – famous for its long sandy beaches that look out to the North Sea – there are worries that the influx will ruin an island idyll.

Calling for “chaos days in Sylt,” one Facebook group said it was time to send a wake-up call to the “Sylt bourgeousie.”

“Come to Sylt with your €9 ticket and go crazy,” the group wrote.

Karl Max Hellner, who owns several fashion shops on the island and belongs to the local business association, said the coming long weekend over Pentecost would be a “stress test” for the island.

Regular commuters from the mainland would find the trains and ferries much fuller than usual, he said.

Ole König, another member of the business association, tried to dispel the image of Sylt as a hideaway of the rich. “This is not a rich zoo where millionaires and billionaires strut around!” he told the Zeit newspaper.

The fears are of a repeat of the disruption caused by radical groups in spring 1995 that was also linked to a cheap weekend travel ticket. At that time, several dozen people were arrested.