A man armed with a handgun threatened and molested an employee at the Hotel Kempinski on the Quai de Mont Blanc at around 3.30pm before making off with an undetermined amount of cash, cantonal police told local media.
“An armed man, apparently with a pistol, was able to flee,” police spokesman Sylvain Guillaume-Gentil told the online site of the 20 Minutes newspaper.
“The amount of his booty remains undetermined,” Guillaume-Gentil said.
The daily said that according to its information the robber targeted a safe at the five-star hotel.
Representatives from the hotel declined to comment.
After the alleged robber fled the hotel on foot, officers in a dozen cars arrived on the scene and a Swiss Army helicopter was pressed into service to track him down.
He was still being sought on Thursday night.
The holdup came a day after Geneva police issued an appeal for witnesses after arresting a suspect following the armed robbery of a business in the Plainpalais neighbourhood on Tuesday.
A man made off with several thousand francs after demanding the contents of a till and a safe from an employee who was threatened with a loaded gun, police said.
Officers later arrested a 25-year-old man, 180 centimetres tall and with a slight build, after removing the key from a scooter that he was driving when he left the motor running at a petrol station.
Police took the key as a precaution to prevent the scooter from being stolen but also to stop the noise that the motor was making, according to a news release.
The suspect, wearing a black helmet, bid the officers good-day but ran from the station when he discovered the scooter key was missing.
Officers later tracked him down.
Police issued a call for witnesses who may have seen the suspect after he fled the petrol station wearing dark trainers, a grey hooded sweatshirt.