The robbery took place around 11.45am at the jeweller’s in the centre of the city at the eastern end of Lake Geneva.
Threatening employees with a hand gun, the trio took valuable jewellery and watches from the shop before fleeing in an undetermined direction, cantonal police said.
The employees, aged 27, 39 and 58, were not injured in the incident but were suffering from shock, police said.
Local municipal forces are cooperating in the case, along with those from neighbouring cantons and Swiss border guards, as well as a canine brigade.
Police said the suspects were talking a Slavic language.
Investigators released a description of the men, all white, along with surveillance video photos of them.
The first suspect was 180 to 182 centimetres tall, around 30 years old and of average build.
With light brown hair and light-coloured eyes, he wore a beard and square-shaped glasses and had areas of redness on his face.
He had a beret, a grey-beige jacket, dark trousers and dark city shoes.
He was carrying a shoulder bag with a white band on the strap, as well as a pistol.
The second suspect was 170 to 175 centimetres tall, 23 to 25 years old, of average build and with a black hat and a dark brown hooded down jacket.
He wore dark blue jeans and dark shoes and was carrying a dark bag.
The third suspect was 170 to 175 centimetres tall, 23 to 25 years old and of average build.
He was wearing a dark cap, a dark hooded down jacket, blue jeans and running shoes with a white stripe on the sole and a red pattern at the rear.
He was also carrying a dark bag.
Anyone who may have information about the suspects is asked to call police at 021 644 44 44 or to contact the nearest police station.