Norway’s intelligence agency raised the national threat level on Sunday after a 17-year-old Russian was arrested on suspicion of placing a homemade bomb in central Oslo.
The domestic intelligence agency PST said an attack was now “probable” rather than “possible”, because of the risk of a copycat attack after recent assaults in Stockholm, Saint Petersburg, London, Berlin and Nice.
The new threat level will be in place for two months.
“It’s not clear whether the 17-year-old young man intended to commit a terrorist attack,” PST chief Benedicte Bjørnland told reporters.
The teen’s lawyer, Aase Karine Sigmond, said her client rejected the allegations, as well as claims in the media that he was an Islamic State (Isis) sympathiser.
“It was a boy’s prank,” she told broadcaster NRK.
The intelligence agency was trying to determine whether he had acted alone.
The incident came after a deadly truck attack that left four people dead and 15 injured in Stockholm in neighbouring Sweden.