She is seriously injured, says Morten Gunneng, duty officer at the police.
A girl of the same age has after a short police operation been arrested suspected of attempted murder.
We have some indications that they have some connection to each other, says Morten Gunneng.
A number of witnesses were present at the scene of the incident and the police are now working on holding interrogations, but the injured girl has not been able to be heard.
Everything suggests that it is a lone perpetrator based on consistent witness statements.
