Finnish police said Saturday that after new information a stabbing spree that left two people dead was now considered a terrorist attack, identifying the suspect as an 18-year-old Moroccan citizen.

Police shot and wounded the knife-wielding suspect on Friday, arresting him minutes after an afternoon stabbing rampage at a busy market square in Turku in southwestern Finland.

"The incidents were initially investigated as murders, but in light of further information received during the night, the offences include now murders with terrorist intent and their attempts," police said in a statement.

The suspect's "identity is known to the police. He is an 18-year-old Moroccan citizen," police said, providing no other details about him.

The number of injured in the attack rose from six to eight and included an Italian national and two Swedes, police said. The other victims were Finns.

Five people were also arrested in a Turku apartment overnight.

"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 (NBI) 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," Laine said.

In June, Finland's intelligence and security agency Supo raised the country's terror threat level by a notch, from "low" to "elevated", the second notch on a four-tier scale.

It said at the time it saw an increased risk of an attack committed by the Islamic State (IS) group.

The agency said it was keeping a particularly close eye on around 350 individuals, an increase of 80 percent since 2012.

"Finland's profile within the radical Islamist propaganda has become stronger. Finland is considered as a Western country and a part of the anti-IS coalition, and propaganda is produced in the Finnish language and directed against Finland. The propaganda incites attacks in Finland," Supo wrote.

- Moroccans in Barcelona, Turku -

It was not yet known whether the Turku attack was related to extremist Islamist circles.

"But if it is related, this is pretty much a continuation of the easy-to-use blatant attacks that Europe has seen," terrorism researcher Leena Malkki from the University of Helsinki told public broadcaster YLE.

Some of the suspects in the twin vehicle attacks in Spain on Thursday that killed 14 people and wounded around 100 others were also Moroccan citizens, but Malkki said there was as yet no reason to believe there was a connection between the Turku and Barcelona attacks.

"The fact that a person is from Morocco is not yet a clue" of a link between the attacks, she said.

"Many European countries are talking about the radicalisation of young Moroccan people."

Media reports in Finland said police believed the suspect had picked his victims at random, but the NBI's Laine could not confirm that.

Police have said it was likely the suspect acted alone, but on Friday indicated they were looking for "other possible perpetrators."

- Flags at half-mast -

Police have said they are collaborating with the Finnish Immigration Service and international authorities in their investigation.

The suspect is meanwhile being treated in hospital in intensive care for a gunshot wound to the thigh.

The motive for the attack was not yet known.

"We haven't yet interrogated the main suspect because of his medical condition," Laine said.

Police also said they had impounded a white Fiat Ducato van suspected of being tied to Friday's stabbing, but provided no other information about how it was linked.

In Friday's attack, bystanders rushed to the scene to help the victims fend off the attacker. At least one of them was stabbed when aiding another person.

According to public broadcaster YLE, five of the injured were to be released from hospital on Saturday.

The interior ministry has ordered flags to fly at half-mast across Finland in honour of the victims.

Immediately after the attack, the Nordic country raised its emergency readiness nationwide, increasing security at airports and train stations and putting more officers on the streets.

On Saturday, a demonstration in memory of the victims was to be held at the Turku market square where the attack took place, organised by Iraqis and Syrians.

On Friday evening, Finnish President Sauli Niinisto attended a vigil in the Turku Cathedral in honour of the victims.

Source: AFP