They said they were acting on information of suspicious individuals thought to be in the city or the area.
Investigations were being carried out to "locate and arrest these individuals", a statement said.
Islamic State militants said they carried out the 13 November attacks on multiple locations, killing 130 people.
Investigations have been launched in several European countries, with two men linked to the attacks - Salah Abdeslam and Mohammed Abrini - still on the run, and others found to have travelled to France posing as refugees.
While Geneva police's statement said that the hunt was related to the Paris investigation, Switzerland's federal police later said it was not linked.
The authorities had gone from a "vague to a precise threat", said Emmanuelle Lo Verso from the Geneva department of security, RTS reported.
In the latest developments:
A conference on Syria's future, involving the US, Russia and the UN, is scheduled to begin in Geneva on Friday, but is not expected to be attended by world leaders.
Some Swiss news outlets say the talks have now been moved from a UN building to an undisclosed location.
The number of police on the streets of Geneva has been increased, so too has their level of alert.
The border with France runs through the outskirts of Geneva and Switzerland is in the Schengen passport-free zone, so the borders are open.
Security at the frontiers was stepped up in the wake of the Paris attacks, as well as at the UN where the world's senior diplomats regularly meet.
But tens of thousands of people cross the Geneva border every day, and checking every car is unlikely to be possible.
In a separate development, police in Belgium had searched three properties in connection with the attacks, the prosecutor's office said.
This week, details emerged of a failed operation involving Belgian and Greek police to capture a suspected ringleader of the Paris terror attacks, Abdelhamid Abaaoud.
Greek authorities had planned to capture Abaaoud in January, when he had been directing a Belgian terror cell from Athens, the BBC has learned.
Police have raised the alert level in Geneva, saying they are hunting for suspects as part of the Europe-wide investigation into the Paris attacks.