"They don't have all the necessary authorisations to operate in the city of Oslo," the city's urban environment head Hans Edvartsen told the e24.no website.
He said they did not have a permit "to manage a reservation platform... and the drivers don't have all the required papers."
As in many other countries, Uber has faced opposition in Norway since its launch on November 19, especially from local authorities and taxi companies.
Founded in 2009, the San Francisco-based firm -- which lets customers hail cars and pay for their journey via Uber's smartphone app -- is now present in more than 200 cities in 45 countries.
The app uses GPS to put customers in contact with the nearest driver, with Uber charging a commission for each journey.
Taxi companies have protested that Uber taxis do not use meters or follow the same regulations that apply to them.
Germany temporarily banned the service in August and a court in Paris ordered the company to pay 100,000 euros in damages for presenting a paid transport service as carpooling.
Danish authorities filed a similar complaint against the service the same day it was launched in Copenhagen on November 19.