The gunmen stole drinks and cash after descending on the main hall of the Reitschule (“Riding school”) where a music and cultural event was going on at around 1am on Sunday, cantonal police said.
The culprits stole money from a cash register from the hall, a 100-year-old building initially used for a riding school, which is used for public gatherings, including a monthly flea market.
An undisclosed amount of money was also stolen from a ticket booth that was damaged, police said.
Several people working at the hall were threatened during the incident and two people were slightly injured.
The masked men did not leave the building until 2.30am, police said.
Police issued an appeal for anyone with information about what happened to phone 031 634 41 11.
Investigators have already interviewed witnesses over the affair.
Police say they are particularly interested in anyone who may have taken photos and videos of the event.