Swedish police say the man suspected of carrying out a truck attack in Stockholm on Friday had been facing deportation.

The 39-year-old Uzbekistan national had expressed sympathy for Islamic State and was wanted by police for failure to comply with a deportation order.

Four people were killed and 15 others were wounded after a man drove a hijacked beer truck into pedestrians and rammed into a department store in the city.

The man was detained in a northern Stockholm suburb on Friday and later arrested on suspicion of having committed a “terrorist crime.”

Jonas Hysing, national head of police operations, said the authorities had been attempting to deport the alleged culprit after his application for permanent residency was refused.

He said police had been attempting to locate him since the Swedish Migration Agency in December gave him four weeks to leave the country:

“He has applied for permanent residence in Sweden; he has been denied that,” he said. “He has been wanted by the police though he has not been in the custody of the Migration Office.”

The police chief said authorities know that he “has expressed sympathy for extremist organizations, among them Islamic State"

No group has yet claimed responsibility for the attack.

It has since been reported that a second man has also been arrested in connection with the attack on suspicion of committing a terrorist offence through murder.

Police remain convinced however that the Uzbek national was the driver of the truck.

Ten people remain in hospital following the attack - two of them in intensive care.

Meanwhile, investigators have confirmed the fatal victims were a British man, a Belgian and two Swedes.

A memorial service was held in the city’s central square this afternoon.

Speaking in the western city of Gothenburg today, Swedish Prime Minister Stefan Lofvren said the country would never be broken by acts of terror.

"We will hunt down these murderers with the full power of Sweden's democracy. There will be no compromises," he said.