BERNE, Switzerland (AFP) - The picturesque heart of Switzerland's capital Berne was locked down on Saturday ahead of a politically-tinged techno parade, with crowds of youngsters preparing to take to the streets for the mass unauthorised rally.
After last year's edition of "Tanz Dich Frei" (Dance Yourself Free) drew huge numbers and saw a minority of black-clad hardliners make for the Swiss parliament to spray slogans on its walls, the authorities were taking no chances.
Barriers were set up on the square in front of the parliament building, and police clad in riot gear deployed at strategic points in Berne's Old Town.
Nearby, around 1,000 people gathered in the early evening around a handful of truck trailers carrying huge speakers which pumped out styles from techno to dub as the crowd began to dance, before the vehicles snaked through the streets.
The event, now into its third year, is tolerated by the authorities even though the organisers lack a permit to hold it.
Given the unseasonal chilly weather in Switzerland it was not clear whether the event's organisers - a collective who mustered participants via Facebook - could repeat the success of the previous edition.
In 2012, some 20,000 people turned out for what was one of the largest youth rallies in the Swiss capital since the 1980s.
To put the number into perspective, Berne's population is close to 126,000.
The organisers' message is political, with banners sporting slogans including "fight for freedom, don't just dance".
In leaflets handed out to participants, they slammed the gentrification of parts of Berne where the alternative scene had thrived, as well as policing policies, neo-liberal economics and commercialism.
On their Facebook page, they told troublemakers to stay away.
"Help one another, keep your alcohol or drug use under control and organise your fights somewhere else. That way, we'll show the police and the authorities we can organise a successful event without them," they said.
Berne's police have been stretched to the limit by the protest, last Monday's trouble at Swiss football's cup final, the security operation for Friday's visit by Chinese Premier Li Keqiang, and another high-tension football match on Wednesday.