Norway said Thursday a bow-and-arrow attack that killed five people appears to have been an "act of terror," with the suspect a Danish Muslim convert previously known to police over fears he had been radicalised.

Four women and a man were killed, and three other people wounded during the rampage on Wednesday in the south-eastern town of Kongsberg in Norway's deadliest attack in a decade.

"There is no doubt that the actual act appears as if it could be an act of terror, but it's important that the investigation continues and that we establish the motive of the suspect," the head of Norway's intelligence service PST, Hans Sverre Sjovold, told a news conference.

Police urged the public to stay at home and several neighbourhoods were cordoned off, with television footage showing ambulances and armed police in the area
Police urged the public to stay at home and several neighbourhoods were cordoned off, with television footage showing ambulances and armed police in the area NTB / HÃ¥kon Mosvold Larsen

Police official Ole Bredrup Saeverud had told reporters earlier in the day the man was believed to be a Muslim convert, adding: "There were fears linked to radicalisation previously."

Police have identified the suspect as Espen Andersen Brathen, a 37-year-old Danish citizen who was a resident of the area, and said he had confessed during questioning.

Reports that linked him to radicalisation pre-date this year, Saeverud said, and police followed up at the time. "We haven't had any reports about him in 2021, but earlier," he said.

"We're relatively sure that he acted alone."

A map locating Kongsberg, Norway
A map locating Kongsberg, Norway AFP / Simon MALFATTO

PST also confirmed the suspect was known to them but declined to disclose further details.

A judge will rule Friday morning whether to remand him in custody and a psychiatric evaluation had begun on Thursday.

Police prosecutor Ann Iren Svane Mathiassen said the evaluation could take "maybe a couple of months".

"This is a person who has been in and out of the health system for some time," Sjovold also told the news conference, confirming the man's mental health was a potential issue.

Police urged the public to stay at home and several neighbourhoods were cordoned off, with television footage showing ambulances and armed police in the area
Police urged the public to stay at home and several neighbourhoods were cordoned off, with television footage showing ambulances and armed police in the area NTB / HÃ¥kon Mosvold Larsen

Norwegian media reported that Brathen was subject to two prior court rulings, including a restraining order against him regarding two close family members after threatening to kill one of them and a conviction for burglary and purchasing narcotics in 2012.

Website Nettavisen published a video Brathen allegedly posted to social media in 2017, in which he issued a "warning" and declared his Muslim faith.

An arrow sticking out of a wall in Kongsberg following the attack
An arrow sticking out of a wall in Kongsberg following the attack NTB / HÃ¥kon Mosvold Larsen

The PST said Wednesday's attack had not raised the general threat level in the country, describing it as "moderate".

"It is our opinion that what happened in Kongsberg yesterday does not warrant changes to the current threat assessment," PST department head Arne Christian Haugstoeyl told reporters.

It was the deadliest attack since far-right extremist Anders Behring Breivik killed 77 people in 2011.

Since then, Norway has seen one other far-right attack, carried out by a self-proclaimed neo-Nazi who opened fire into a mosque.

A map locating Kongsberg, Norway
A map locating Kongsberg, Norway AFP / Simon MALFATTO

Kongsberg, a picturesque town of 25,000 people with wooden facades and the foliage changing colour for the autumn, was largely quiet on Thursday.

Knut Olav Ouff, 54, told AFP he was about to light a cigarette on the doorstep when he found himself in the middle of the tragedy.

"I saw a friend of mine cowering behind a car and then suddenly heard a 'thung'," he said. "I could hear the tinkling of the arrow hitting the streets. And after that I could see a man drawing a kid out of a car and running towards my house."

Streets were almost empty Thursday with only a light police presence.

A few police officers stood outside a store where part of the attack took place. A glass door there was chipped by a shot.

Candles flickered outside the town's church.

The victims have not yet been named publicly, but one of the wounded was an off-duty police officer who had been in a store.

Norwegian media questioned why it took police more than a half-hour to arrest the suspect after the first reports of the attack.

Police were informed of the attack at 6:13 pm (1613 GMT) and the suspect was arrested at 6:47 pm. He fired arrows at police, who responded with warning shots, Saeverud said.

Images in the media showed a black arrow sticking out of a wall and what looked like competition-grade arrows lying on the ground.

Police said Thursday the suspect had also used other weapons, but provided no details.

A neighbour who requested anonymity decribed the suspect as a big person with short hair and a serious demeanor, who was always seen "alone".

"No smile, nothing in the face. He was just staring," the neighbour told AFP.

Norwegian police are not normally armed, but after the attack, the National Police Directorate ordered that officers be armed nationwide.

Norway rarely experiences such violence, but 10 years ago Anders Behring Breivik killed 77 people in the country's worst massacre since World War II.

Several planned jihadist attacks have also been foiled by security services.