Norwegian authorities have arrested a 17-year-old who is suspected of planning a terrorist attack inspired by the Islamic State (IS).

The teenager, who was born in Norway, reportedly expressed support for IS and was seen carrying the group’s flag at school. He was detained on Thursday by Norway’s PST, the country’s internal security and counter-terrorism service, and was placed in provisional custody for two weeks.

Line Nyvoll Nygaard, a senior official at PST, said the teen is suspected under the section of the criminal code that covers preparation of terrorist acts. The agency has not released further details, citing an ongoing investigation.

The youth’s lawyer, Knut Lerum, confirmed that his client denies the allegations.

Documents cited by NRK indicate that the teenager allegedly planned to attack NATO’s Joint Warfare Centre in Jåttå, Stavanger. Founded in 2003, the centre trains senior officers from alliance countries and coordinates military exercises.

The arrest took place in the southwestern Rogaland region, near Stavanger. Norwegian authorities continue to investigate the case.