A man armed with a bow and arrows killed five people and wounded two others on Wednesday in southeastern Norway, police said, adding that they had arrested the suspect.
The motive for the attack, which took place in several locations in the center of Kongsberg, was not yet known, but police said terrorism could not be ruled out.
Local police official Oyvind Aas confirmed that five people were dead. The two wounded were in critical care units in the hospital but their lives did not appear to be in danger, he told a news conference.
One of the wounded was an off-duty police officer who had been in a store, one of the several places attacked.
The suspect "has been arrested by the police and, according to our information, there is only one person involved," Aas told the news conference.
He said that "given how events unfolded, it is natural to assess whether this is a terrorist attack."
"The arrested man has not been interviewed and it is too early to say anything about his motives," he said, adding that "all possibilities were open."
Norway's intelligence service PST had been alerted, spokesman Martin Bernsen told AFP.
"It is all conjecture at the moment," he said when asked about the possibility of a terrorist motive.
Police said the suspect had been taken to a police station in the nearby town of Drammen but gave no other details about the man, including whether he had previously been known to the authorities.
Police were informed of the attack at 6:13 p.m. local time (1613 GMT) in the town of 25,000 people, around 80 kilometers (50 miles) west of the capital Oslo. The suspect was arrested at 6:47 p.m.
U.N. Secretary-General António Guterres said on Twitter that he was "shocked and saddened" by the tragedy.
"These events shake us," said Prime Minister Erna Solberg on her last day in office.
On Thursday she will hand over the prime ministership to Jonas Gahr Store, whose Labour Party won parliamentary elections on September 13.
The scene of the attack was blocked off by police, an AFP correspondent said.
Police urged the public to stay at home and several neighborhoods were cordoned off, with television footage showing ambulances and armed police in the area.
Police in the Scandinavian country are not normally armed, but after the attack the National Police Directorate ordered that officers be armed nationwide.
A helicopter and bomb disposal team were also sent to the scene.
The website of public broadcaster NRK published an image sent by a witness of a black arrow sticking out of a wall.
In other pictures from the scene, what looked like competition-grade arrows could be seen on the ground.
Norway suffered one of history's worst mass shootings on in July 22, 2011, when right-wing extremist Anders Behring Breivik killed 77 people.
Breivik first set off a bomb in Oslo next to the building that housed the office of the prime minister, then went on a shooting spree at a summer camp for left-wing youths on the island of Utoya.
In another right-wing attack, self-proclaimed neo-Nazi Philip Manshaus opened fire into a mosque on the outskirts of Oslo in August 2019 before being overpowered by worshippers, with no one being seriously injured.
However, he had earlier shot dead his step-sister, who had been adopted from China, in what prosecutors termed a "racist act."
Several planned jihadi attacks have also been foiled by security services.