OSLO An Oslo court heard arguments on Monday on whether to let Norwegian police keep detaining a Russian teenager as they investigate suspicions that he was plotting an attack with a "bomb-like device".
The 17-year-old was detained on Saturday night, accused of possessing a primitive explosive device in Oslo in what his lawyer said was a mere "boyish prank". The bomb squad used a robot to blow up the small object and no one was hurt.
Police across the Nordic region went on heightened alert after four people were killed when a hijacked truck ploughed into them on a shopping street in Stockholm on Friday, in what Swedish police said appeared to be an Islamist militant attack.
In Oslo, police lawyers want Oslo district court to let them detain the Russian youth for two weeks, the maximum period allowed for a minor under Norwegian law, while they investigate under anti-terrorism laws.
Police said the motive of the youth, whose name has not been released, was still not known and that it was unclear whether he had acted alone.
Wearing a yellow jumper with thin horizontal grey stripes, the teenager appeared impassive, sometimes leaning towards his lawyer to talk. Most of the hearing was conducted behind closed doors at his and the authorities' request.
Outside the courtroom, armed police searched belongings of audience members - a rare display of high security in the Nordic country.
After a suspected supporter of Islamic State rammed a hijacked beer delivery truck into street crowds in Stockholm, Norway's PST security police raised the risk of an attack in Norway to "probable" from "possible".
The youth's lawyer said he was not an extremist.
"He says he is not guilty. He disagrees with Islamists and is against violence. He had not planned to hurt anybody," Aase Karine Sigmond told Reuters. "This was a boyish prank ... He is very upset at being detained."
The youth, from Russia's southern Caucasus region, came to Norway as a 10-year-old with his family and had applied for asylum. He had been an active member of a wrestling club in Arctic Norway before moving south to attend high school.
The PST said it had been in "preventive" contact with the teenager earlier after concerns were raised that he may have been radicalised and was drifting towards militant Islam.
But a man who used to train at the same wrestling club told Reuters: "He was a normal boy. He went to school and went home to his family. There was nothing extreme about him."
The youth was detained on Saturday night after a witness alerted police to a person on his knees holding a suspicious package beside a car in a dark street.
"If it was a bomb he had made, I would be surprised if he was completely alone," Thomas Hegghammer, a researcher at the Norwegian Defence Research Establishment who focuses on violent Islamism, told Reuters. "It is not easy to build a bomb."
(Additional reporting by Camilla Knudsen; editing by Mark Heinrich)