STOCKHOLM: The suspect in Stockholm's deadly beer truck attack is a 39-year-old native of Uzbekistan who had been on authorities' radar previously, Swedish authorities said on Saturday.
Prime Minister Stefan Lofven urged citizens to "get through this" and strolled through the streets of the capital to chat with residents and offer reassurances after what he called "a terror attack".
Flags flew at half-staff to commemorate the four people killed and 15 wounded when the hijacked truck ploughed into a crowd of shoppers on Friday afternoon in Stockholm. The prime minister declared Monday a national day of mourning, with a minute of silence to be marked at noon.
Sweden's police chief said authorities were confident they had detained the man who carried out the attack.
"There is nothing that tells us that we have the wrong person," Dan Eliason told a news conference on Saturday, but added he did not know whether others were involved in the attack. "We cannot exclude this."
Eliason also said police found something in the truck that "could be a bomb or an incendiary object, we are still investigating it".
Prosecutor Hans Ihrman said the suspect had not yet spoken to authorities and could not confirm whether he was a legal resident of Sweden. Anders Thornberg, head of the Swedish Security Service, said security services were working with other countries' security agencies to investigate the attack, but declined to elaborate.
Police declined to comment on media reports about overnight police raids around Stockholm or if they were hunting any more suspects in the case. They said the suspect had been on their radar before but not recently, and did not explain why authorities apparently had not considered him a serious threat.
Eliason told reporters the suspect was "a more marginal character".
Sweden's health service said 10 people were still being treated in hospital for wounds and four of them were seriously injured.
Many in Sweden were shocked by the attack, questioning whether Swedish society -- considered democratic and egalitarian -- had failed in some way.
Visiting the attack site at an upscale department store, Crown Princess Victoria laid roses on the ground and wiped away a tear. "We must show a huge force, we must go against this," she told reporters.
The stolen beer truck travelled for more than 500 metres along Drottninggatan, a main pedestrian street, before smashing into a crowd outside the popular Ahlens department store around 3pm local time on Friday.
The crash was near the site of a December 2010 attack in which Taimour Abdulwahab, a Swedish citizen who lived in Britain, detonated a suicide bomb, killing himself and injuring two others.