STOCKHOLM • The suspect in the Stockholm truck attack was known to have expressed sympathies with extremist groups, including the Islamic State in Iraq and Syria (ISIS).

Police said yesterday that the suspect had sought and been denied permanent residency in the Nordic country, and was wanted for deportation. "We know that he showed sympathies for extremist organisations, among them ISIS," national head of police operations Jonas Hysing told reporters .

Police said roughly five other people remained in police custody for questioning over the apparent terror attack, in which a hijacked delivery truck mowed down pedestrians in Stockholm last Friday, killing four people.

A 39-year-old Uzbek man was arrested as the suspected driver.

A further 15 people were injured when the beer delivery truck barrelled down a busy shopping street before crashing into a department store and catching fire.

Several raids were conducted around Stockholm at the weekend. Mr Hysing said "the evidence looks very strong" that the Uzbek man was the driver of the hijacked truck.

There has been no immediate claim of responsibility for the Stockholm attack - the third in Europe in two weeks, coming on the heels of the car-and-knife assault outside London's Parliament and the St Petersburg metro bombing.

Stockholm was returning to normal yesterday, with police barricades taken down along Drottninggatan Street, where the attack took place. Hundreds of flower bouquets covered the steps leading down to the square next to where the truck ploughed into the Ahlens department store, with more piled up under boarded-up windows.

Ten of the injured people remained in hospital, with two of them in intensive care, the authorities said. Police said they had identified three of the four dead.

A memorial service was held yesterday in Sergelstorg, the central square next to Drottninggatan.

Swedish Prime Minister Stefan Lofven, who beefed up border controls last Friday after the attack, announced a national minute of silence to be observed in honour of the victims at noon today.

"Today, all of Sweden is in mourning but we are going to get through this together," he said last Saturday.

REUTERS, AGENCE FRANCE-PRESSE