The 80 new cases follow 47 cases the preceding day, according to Oslo Municipality figures.
Daily cases in the capital have generally remained between 40 and 50 since late September. The city introduced at the end of last month local measures to reduce infections in the area.
The latest round of infections has resulted in 200 residents of the Blindern Studenterhjem being asked to quarantine, NRK reports.
The city is to consider whether new measures or restrictions are necessary in response to the latest data, the broadcaster writes.
Although the government will ease national restrictions in October, measures put in place by local authorities will take precedence over the national rules.
Oslo already has stricter rules than the rest of the country, including a ban on public gatherings of over 10 people. The national rules stipulate a maximum of 20 people for such gatherings.
An update on the Oslo restrictions is expected to be given by the city authorities later on Thursday.