Police in Finland say the stabbings in the city of Turku yesterday are being treated as terrorism.
They said the suspect is an 18-year-old Moroccan man, who was shot in the leg and arrested.
Two people were killed and eight injured in the attack.
Police have revealed that both of the fatalities were Finnish. Among the injured were two Swedes and one Italian.
Due to info received during the night, the Turku stabbings are now investigated as murders w/ terrorist intent (2) and their attempts (8).
— Keskusrikospoliisi (@krp_poliisi) August 19, 2017
Terrorist attack
"The act had been investigated as murder, but during the night we received additional information which indicates that the criminal offences are now terrorist killings," police said in a statement.
"The suspect's identity is known to the police. He is an 18-year-old Moroccan citizen," it said.
Finnish police also arrested five people in a Turku apartment overnight in connection with the stabbings.
"There was a raid and we have now six suspects in custody, the main suspect and five others," Detective Superintendent Markus Laine of the National Bureau of Investigation told AFP.
"We are investigating the role of these five other people but we are not sure yet if they had anything to do with [the attack].
"We will interrogate them, after that we can tell you more. But they had been in contact with the main suspect," Mr Laine said.
The main suspect is being treated in hospital in intensive care for a gunshot wound to the thigh.
Motive
Media reports in Finland said police believed the suspect had picked his victims at random, but Mr Laine could not confirm that.
Police have said it was likely the suspect acted alone, but added they were looking for "other possible perpetrators."
Central Turku was quickly cordoned off after the attack, which occurred just after 4pm local time (1300 GMT).
The attack in Finland came a day after two terror-related attacks in Spain - one in Barcelona and one in Cambrils.
Four men, aged 21, 27, 28 and 34, have been arrested in connection with those attacks and remain in custody.
Three are Moroccan and one is Spanish.
