At least one person was killed, and five were severely wounded, during a Sunday morning shooting at a Swiss nightclub in the city of Aarau, local authorities said.
According to reports by the Swiss newspaper Blik, one person was killed when gunmen entered the party, which was being held at the city's horse racing track.
Blik also reported that the victim who was killed was a 22-year-old woman identified only as "M." by the party organizers.
According to Italy’s Foreign Ministry, the one victim who was killed was an Italian citizen.
"Nighttime shots at event in Schachen. Several victims. Major police operation underway. Stay away from the area," said the police in a statement.
"Due to the ongoing major police operation, Aarau Swimming Pool will remain closed until further notice. Visitors are requested to stay away from Aarau Schachen," it added in a statement later.
All the victims are Swiss residents and in their 20s, police said, adding that a manhunt was underway and large areas of the town had been cordoned off. They appealed to the public for any images of the incident.
Several people reportedly wounded, at least one dead
According to the report by Blik, one of the partygoers said that people believed that the first shots fired were actually fireworks.
"We noticed that there was a shooting when someone yelled: 'Everyone down,'" he told the Swiss outlet, while he also detailed that his group had to hide under the DJ booth.
The report also noted that one person was killed, according to a witness, with one of the partygoers attempting to resuscitate a victim with several wounds.
"It's just incredibly tragic. She was young," a 34-year-old witness who asked for anonymity told Reuters. "That something like this could happen in Aarau, at a local event, is simply unimaginable. I still can't really process it."
This is a developing story.