Several people were stabbed near a shopping centre in the Finnish city of Tampere on Thursday, police said.
Police said in a statement they had arrested one person and that the situation no longer posed a danger to others.
The injured are being given first aid, the police said.
They did not give details on the extent of the injuries nor on the perpetrator.
Police said they were interviewing witnesses and had cordoned off the scene.
Public broadcaster YLE reported that traffic in the centre of Tampere - located some 180 kilometres (112 miles) north of Helsinki and the country's third-largest city - is at a standstill.
Local paper Aamulehti reported that the person arrested was a man.