Police confirmed they have received 22 reports from women saying they have been attacked during the We are Stockholm event.
Officials said seven complaints came on the festival’s first day on Tuesday this week, with another 15 reported by Thursday.
Stockholm police added the figure was expected to increase as the event is still ongoing.
They also refused to disclose the nationality of the suspected assailants.
Police spokesman Kjell Lindgren said: “Many report the incidents a while after the assault happened, so there is reason to believe the figure will increase.”
The official said the majority of the reports had involved men groping girls in the crowd.
Mr Lindgren added police had identified the assailants in about half the reported incidents as he said it is believed the same person had committed several assaults.
Police officer Mats Eriksson said the reported attacks had happened while the artists were on stage.