A man stabbed eight people Friday in Finland's western city of Turku, killing two of them, before police shot him in the thigh and detained him, police said. Authorities were looking for more potential suspects in the attack.

A suspect — a man whose identity was not known — was being treated in the city's main hospital but was in police custody. Security was being stepped up across the Nordic country, Interior Minister Paula Risikko told reporters at a news conference.

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Rescue personnel at the location where several people were stabbed, at Turku Market Square, Finland. (Lehtikuva/Roni Lehti/Reuters)

Police did not give any information on the two people killed or the conditions of those wounded in downtown Turku, 150 kilometres west of Helsinki.

Finland's top police chief, Seppo Kolehmainen, said it was too early to link the attack to international terrorism.

"Nothing is known about the motives … or what precisely has happened in Turku," he said.

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An armed police officer secures the area following the stabbing attack in Turku. Security was stepped up across the country, officials said. (Roni Lehti/Lehtikuva via AP)

It was not known if Friday's attack was somehow linked to a decision in June by Finland's security agency to raise its threat assessment to the second level of a four-step scale. The Finnish Security Intelligence Service says the country's "stronger profile within the radical Islamist propaganda" led to the change. It said the Nordic country is now considered part of the coalition against the Islamic State group.

Police said late Friday that they believe the man they have in custody acted alone. 

"At this stage, there is only one suspect and we are investigating whether there are more people involved ... but it looks likely [he was alone]," Markus Laine from the National Bureau of Investigation said.

"For now we do not investigate this [as a terrorist attack] but the possibility has not been ruled out," he told a news conference.

Other arrests made

Late Friday, local media reported that Finnish police had raided an apartment in eastern Turku and were "quite certain" police had identified the attacker.

The raid occurred just before 10 p.m. local time after police located a suspected vehicle, a white Fiat Ducato, whose owner lived in a building located in Turku's Varissuo suburb, Finnish newspaper Ilta-Sanomat reported.

A number of people were arrested during the night, as the Nordic country investigated their possible link to the attacker, Finnish news agency SST said.

"We are investigating what their role is in this. Whether they had something to do with this act, or if they were just involved with this person [the suspect]," Det. Supt. Markus Laine was quoted saying of those arrested.

It was unclear if any of the arrests happened in the raided apartment.

Varissuo suburb, Turku's largest, is home to a large immigrant population and is located about seven kilometres away from the market square where the attack took place

'He was waving it in the air'

The Ilta-Sanomat tabloid said six people were injured in the attack, one man and five women, and that a woman with a stroller had been attacked by a man with a large knife. Finnish broadcaster YLE said several people were seen lying on the ground in Puutori Square after the attack.

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A general view shows Turku Market Square, where several people were stabbed Friday in Finland. (Vesa Moilanen/Lehtikuva/Reuters)

Witness Laura Laine told YLE she was about 20 metres from where the stabbing took place.

"We heard a young woman screaming. We saw a man on the square and a knife glittered. He was waving it in the air. I understood that he had stabbed someone," Laine was quoted as saying.

Finland's government was closely monitoring the police investigation into the attack, Prime Minister Juha Sipila said.

Finnish President Sauli Niinisto arrived at Turku later Friday and condemned the attack as "a shocking and cowardly act."

"This attack touches us all deeply," said Niinisto.

The country's political leaders and security officials are doing their utmost "so that all Finns are able to feel safe," he said.

"Police have told us not to go to the city centre, so we are in this coffee shop a few blocks away," said Vanessa Deggins, an American studying business at one of Turku's three universities, told The Associated Press. She didn't witness the attack, but heard sirens going past.

"This is a safe country by American standards. I have gone home alone at 2, 3 a.m. ... I feel safe," she said.

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The stabbings occurred in Turku in southwest Finland. (Google)

With files from Reuters