The criminal suspicion concerns preparation to commit an act of terrorism, says PST's head of preliminary investigation, Line Nyvoll Nygaard.
The first interrogation of the 17-year-old is said to have been held, but it is not clear how he responded to the accusations. Some form of seizure has been carried out.
Authorities have requested that the boy be detained on the grounds that he is considered able to influence the evidence. PST would not say more about the suspicions at this stage.
The arrest took place in Rogaland county, which is located along Norway's North Sea coast, south of Bergen.
