Police in Sweden said on Sunday that the suspect in the Stockholm truck attack was known to have expressed sympathies with extremist organisations, including the so-called Islamic State.
They said he had sought and been denied permanent residency and was wanted for deportation.
A court official said on Sunday that a second person had been arrested and had been assigned a lawyer. Earlier the authorities said seven people had been brought in for questioning over the attack.
The four people who died were two Swedes, a Briton and a Belgian, according to the authorities.
On Saturday police confirmed a suspect device was found in the hijacked lorry that ploughed into a Stockholm department store on Friday.
They have not given details about the exact nature of the device, but say it was discovered in the driver’s seat.
A 39-year-old Uzbek national is being detained on terrorism charges. He is suspected of deliberately driving the beer delivery truck into crowds in the capital, killing four people and wounding 15.
The man was already known to Swedish intelligence services as a marginal figure.
Sweden’s National Police Chief Dan Eliasson gave the following statement:
“We are focusing on, of course, how he has entered the country, where he has been, the type of contacts he had, what can we see from his friends and so on.”
King Carl Gustaf and other members of the Swedish royal family have paid tribute to the victims of the attack.
A child is among ten people who remain in hospital, two of whom are in intensive care.
A memorial service will be held on Monday (April 10) and Sweden will observe a minute of silence for those killed and injured.