“The man has been apprehended … from the information we now have, this person carried out these actions alone,” police chief Oeyvind Aas told reporters.
“Several people have been injured and several are dead,” Aas said. He declined to comment on the number of casualties.
Following the attacks, the police directorate said it had immediately ordered officers nationwide to carry firearms. Norwegian police are normally unarmed but officers have access to guns and rifles when needed.
“This is an extra precaution. The police have no indication so far that there is a change in the national threat level,” the directorate said in a statement.
The attacks took place over “a large area” of Kongsberg, a municipality of around 28,000 people in southeastern Norway, police said.
“This is a gruesome incident, there is nothing else to say. Now we must try to take care of the inhabitants as best we can,” town mayor Kari Anne Sand told TV 2.
She said that the attack took place in the Vestiden area, which has housing, shops and a university campus.
Norway’s minister of justice and public security, Monica Maeland, has received updates on the attacks and was closely monitoring the situation, the ministry said.