“Searches to find the perpetrators, who are currently unknown, are under way,” it added.
“Any possible motives as well as the exact circumstances of the act remain to be clarified.”
Contacted by AFP, police were unable to say how many suspects there were nor the type of firearms used in the shooting.
A large-scale police operation swung into action in the area and beyond “as a precaution”, the authorities said.
An AFP journalist saw armed officers deployed on the highway up to 30 kilometres (18 miles) from the site of the shooting.
‘Several shots’
Media reports said an army helicopter was deployed in the cantonal capital, Aargau, as well as numerous police officers, rescue workers and medical teams.
Swiss news agency ATS-Keystone reported that police were alerted about gunshots during the night while police spokesperson Vanessa Rumpold told the Blick newspaper that “several shots” were fired at a large group of people.
Witnesses told Blick that shots were fired at about 2:30 am while the rave was still taking place. Initially, they were believed to be fireworks but one witness reported “shots fired in bursts”.
Many people sheltered in a nearby gymnasium for safety.
A local resident in Aarau posted a video on social media showing deserted streets and what sounded like several gunshots in the background.
The Aargau cantonal police urged people to stay away from the area and asked for video recordings or photos from the rave.
The scene around the shooting was cordoned off on Sunday.
All of the victims were Swiss residents, police said.
Army reservists in Switzerland are allowed to keep their weapons, but not ammunition, at home. As a result, weapons are widespread but with no federal register it is difficult to know exactly how many.
According to the Geneva-based research centre Small Arms Survey, civilians had more than 2.3 million firearms in 2017 – nearly three for every 10 inhabitants.
That made Switzerland the 16th country in the world in terms of weapons per capita.
– AFP
