Finnish police are investigating Friday's knife attacks that killed two and wounded eight in the city of Turku as crimes related to terrorism, they said on Saturday.
The suspect was an 18-year Moroccan, police added. The two people killed were Finns and an Italian and two Swedish citizens were among the injured.
"Due to information received during the night, the Turku stabbings are now being investigated as murders with terrorist intent," the National Bureau of Investigation said in a statement.
Following the attacks on Friday, police shot the suspected attacker in the leg and arrested him.
Security was reinforced nationwide with increased patrols and more surveillance in case more people were involved.
The police will hold a press conference at 1100 GMT.
Flags were at half mast on Saturday across the Nordic country where violent crime is relatively rare. Still, the Security Intelligence Service raised the terrorism threat level in June to 'elevated' from 'low', saying it had become aware of terrorism-related plans in Finland.