OSLO — The man accused of being behind Wednesday's deadly bow-and-arrow attack in Norway is a Muslim convert who had previously been flagged as having been radicalized, police said.

"There earlier had been worries of the man having been radicalized," Police chief Ole B. Saeverud told a news conference on Thursday morning.

Five people were killed in the attack in Kongsberg, and two others were seriously injured.

Norway's acting Prime Minister Erna Solberg described the attack against shoppers in the town, near Oslo, as "gruesome".

"It is a very dramatic situation that hits the community in Kongsberg hard. The events shake us. I understand that many are afraid," she said.

The police said on Wednesday evening that a person had been seen shooting people with a bow and arrow in central Kongsberg, and they warned people to stay indoors.

Officers first received reports of an attack from people in the town’s center shortly after 18.00 local time.

The suspect was apprehended around 30 minutes later. He was taken to a police station in nearby Drammen.

"We will return to a more detailed description of the course of events when we have a better overview of what happened," said police inspector Oeyvind Aas. "It goes without saying that this is a very serious and extensive situation."

Police have confirmed that five people — four women and one man between the ages of 50 and 70 — were killed in the incident.

Two other people were injured and are in intensive care in hospital. One of those injured was an off-duty police officer, who was found in a supermarket, one of multiple locations where the attack took place in Kongsberg.

Police said overnight on Wednesday that they had charged a man over the attack. He is a 37-year-old Danish citizen living in Kongsberg.

Earlier, law enforcement said they believed he was the sole attacker.

"Based on the information we have now, this is a person who has carried out these actions alone," Aas told a news conference.

He said there was no active search for any more suspects.

Police say the motive for the attack is still being determined and that terrorism had not been ruled out.

The prime minister-designate, Jonas Gahr Stoere, who is expected to take office on Thursday, called the assault “a cruel and brutal act” in comments to Norwegian news agency NTB.

Solberg, Norway's outgoing PM, said: "A man has killed several people in Kongsberg and several are injured. Police confirm that the perpetrator has been arrested. As far as the police know now, the perpetrator was alone. It is important to emphasize that there is much we do not know yet. It is too early to say anything about the motive behind the actions, but the police are considering whether it is a terrorist act.

"The messages coming from Kongsberg tonight are gruesome. The perpetrator has carried out horrific acts against several people. It is a very dramatic situation that hits the community in Kongsberg hard. The events shake us.

"I understand that many are afraid. Therefore, it is important to emphasize that the police are now in control of the situation. Our thoughts go first and foremost to those affected and to those closest to them." -- Euronews