The Unspunnen festival is a celebration of Swiss folklore
A historical stone symbolising Swiss national unity has been stolen from a hotel in the central Swiss city of Interlaken where it was on display.
The 80kg (165lb) stone, called Unspunnenstein, had already been stolen once in 1984, by an underground group from the francophone region of Jura.
The group has not made an outright claim this time, but issued a statement in support of the theft of the boulder.
It was to be the centrepiece of a festival due to take place next month.
The festival would have marked the stone's bicentenary.
The event, which includes yodelling, Alphorn playing, dancing and wrestling in lederhosen, revolves around and is named after the traditional stone-throwing competition.
It first took place in 1805, at a gathering in Unspunnen near Interlaken to assert Swiss national identity in the face of Napoleon's advances.
Contestants lift the stone above their head and hurl it as far as they can, taking care not to step over a board.
The theft early on Sunday morning was witnessed by an employee in the lobby of the luxury hotel where it was being kept.
The four male thieves left behind a brick carrying the emblem of the neighbouring region of Jura.
A separatist movement, known as Belier, later issued a statement saying: "It is obvious the Unspunnen stone is again in Jurassian hands."
The group would like a part of the Jura hills which is still under the jurisdiction of the German-speaking Bern canton to be integrated into the francophone Jura canton.