Another teenager, who is also under 18, has been arrested in connection with the episode.
Police will try to get the main suspect produced on Saturday in constitutional interrogation for the stabbing, the central head of investigation informs.
Copenhagen Police received the report of the episode at 02.25.
The main suspect was arrested when the police arrived at the apartment, which is located on Lundtoftegade in Nørrebro.
Chenette Westergaard does not want to comment on a possible motive and the course of events, as the police are still investigating.
Witnesses are also still being sought.
It is assumed that the two boys know each other.
Source: The Nordic Page