Five people have been killed and two more injured in Norway after a man used a bow and arrow to attack them.

Police first received word of an attack in the town of Kongsberg, south-west of the capital Oslo, at 18:13 local time (16:13 GMT).

A Danish man aged 37 has been arrested on suspicion of carrying out the attack.

Police believe he acted alone, and will investigate whether it was an act of terrorism, a spokesman said.

Prime Minister Erna Solberg said reports of the incident had been "horrifying".

"I understand that many people are afraid, but it's important to emphasise that the police are now in control," she told a news conference, hours before she was due to leave office.

The attacker is said to have launched the assault inside a Coop Extra supermarket on Kongsberg's west side. One of those injured was an off-duty police officer who was in the shop at the time.

A spokesperson for the chain later confirmed a "serious incident" at their store, adding that none of their staff were physically injured.

Local police chief Oyvind Aas confirmed that the attacker had managed to escape an initial confrontation with police before an arrest was finally made at 18:47 local time, 34 minutes after the attack began.

One witness told local outlet TV2 she had heard a commotion and seen a woman taking cover, then a "man standing on the corner with arrows in a quiver on his shoulder and a bow in his hand".

"Afterwards, I saw people running for their lives. One of them was a woman holding a child by the hand," she added.

Police have told the Norwegian news agency NTB that the attacker also used other weapons during the incident, without giving more details on what they were.

The suspect moved over a large area, and authorities cordoned off several parts of the town. Residents were ordered to stay indoors so authorities could examine the scene and gather evidence.

Kongsberg Mayor Kari Anne Sand said it was a shocking attack that had taken place in an area where many people lived, and that a crisis team would help anyone affected.

The suspect was taken to a police station in the town of Drammen, where his defence lawyer, Fredrik Neumann, said he was questioned for more than three hours and was co-operating with authorities.

He added that the suspect has a Danish mother and Norwegian father.

Norway's Justice Minister Monica Maeland told reporters the police did not yet know whether or not it was act of terrorism and could not comment on details emerging about the suspect.

Police prosecutor Ann Irén Svane Mathiassen told TV2 that the man had lived in Kongsberg for several years and was known to police.

The attack came on the final day of Erna Solberg's conservative government, and a new justice minister will take over the case on Thursday under a centre-left coalition led by Labour leader Jonas Gahr Store.

Mr Store said it was a "gruesome and brutal act".

Norway's police directorate has ordered all officers nationwide to carry firearms as an extra precaution. Usually police in the country are not armed.

"The police have no indication so far that there is a change in the national threat level," the directorate said in a statement (in Norwegian).

The attack was Norway's deadliest since far-right extremist Anders Behring Breivik murdered 77 people, most of them at a children's Labour Party summer camp on the island of Utoya in July 2011.