Swiss rave shooting suspect has 'psychological problems': prosecutor

The man suspected of shooting dead an Italian woman at a rave party in Switzerland is suffering from "psychological problems" and has remained silent in custody, prosecutors said Wednesday.

Gunfire erupted in the early hours of Sunday morning as an annual rave was winding down at the racecourse in Aarau, capital of Switzerland's northern canton of Aargau.

The attack left a 22-year-old Italian woman dead, and five others were taken to hospital with gunshot wounds.

A 43-year-old Swiss man who lives in northwestern Switzerland's Jura canton handed himself in to police in Delemont, the region's main town.

He is suffering from "psychological problems", and has maintained his silence since his arrest on Monday, Aargau cantonal prosecutor Christoph Ruedi told a press conference.

The man has offered no explanation of events, but "provided some information regarding his personal situation" that "suggests he may be suffering from mental health issues" which require further examination, said Ruedi.

The Aargau police said that two pistols and an AK-74 assault rifle were found in the suspect's vehicle.

Reporters were told that the initial forensic analysis showed matching characteristics between the weapons seized and the cartridge cases found at the scene.

Police chief Michael Leupold said the motive for the attack remained unclear, adding that the suspect was not previously known to the police and had no known links to extremist movements.

"To date, we have absolutely no evidence of any history of violent extremism or ideological affiliation," he added.

The police said the shooter acted alone and fired around 40 rounds with the rifle, then continued shooting with a pistol before fleeing in his vehicle.

Evidence from the crime scene suggests the shooter fired indiscriminately at the festival site from various positions outside the grounds, they said.

The five taken to hospital were four Swiss men and a German woman, aged between 24 and 31.

The police said Wednesday that two of them were still in hospital, but their lives are no longer in danger and they should be able to be discharged in the coming days.

Another person has since come forward who sustained a minor injury, possibly from a ricocheting bullet, they added.

And at least one bullet hit a car containing four people as it was driving away.

"All indications suggest that all these people were random victims," the police said, adding that it remained unclear why the shooter targeted the rave event, with investigators finding he had no geographical or personal links to Aarau.

Shootings are rare in Switzerland, despite widespread gun ownership.

Leupold said the suspect had acquired his weapons privately, with the approval of the Jura authorities, around 20 years ago.

Flowers, candles and notes have been left at the gates of the racecourse, where the Swiss flag was flying at half-mast.