According to the public broadcaster, the suspect, who was born and grew up in Norway, had been seen in school with an IS flag.

He was arrested on Thursday by officers from Norway's PST internal security service, which is responsible for counter-terrorism, before being taken into provisional custody for two weeks on Friday.

His lawyer, Knut Lerum, told AFP that he denies the accusations.

According to the NRK, citing PST documents, the teenager was planning to detonate explosives at NATO's Joint Warfare Centre in Jatta, Stavanger, in southwestern Norway.

The PST had yet to reply to an AFP request for comment.