Around 300 people gathered at Vidy beach in Lausanne on Saturday for an anti-fascist picnic, two weeks after a 35-year-old man was attacked there by neo-nazi assailants in broad daylight.
The victim, who was wearing a t-shirt reading "Antifa", needs surgery for facial fractures.
Organisers say the incident points to a growing normalisation of far-right violence in the region.
Four suspects have been identified: three men in Vaud and a 16-year-old in Valais, all placed in provisional detention. The Vaud prosecutor's office has opened a criminal investigation.
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