The annual Fetes de Bayonne in the Basque country on the Atlantic coast is one of France’s biggest summer festivals with events ranging from music to bullfighting and over a million people participating.

READ MORE: La corrida: Why south-west France’s Bayonne Festival is controversial

The four complaints over rapes “in public places or in apartments”, some of which could already be “clearly established”, have prompted the opening of investigations, Bayonne deputy prosecutor Caroline Parizel told reporters after the five-day festival concluded.

The suspects have not yet been identified, she said.

An attempted murder investigation has also been opened after an attack on a 46-year-old man by three individuals who remain at large, she added.

As with similar events elsewhere in Europe, efforts have been made in recent years to prevent sexual violence at the festival.