Two people were wounded in central Stockholm on Saturday in what appeared to be the first suicide bombing in the history of Sweden, which has been spared the major terrorist strikes seen in several other European countries.
A car exploded in the middle of the seasonal shopping frenzy, shooting flames and causing several smaller blasts as people ran screaming from the scene. The blast that killed the alleged bomber came moments later a few blocks away from the car explosion on a busy pedestrian street.
Experts said the alleged bomber probably didn't succeed in detonating all the explosives and could have caused much greater damage.
Although police haven't confirmed Saturday's attack was motivated by extremist views, an audio file sent to Swedish news agency TT shortly before the blast referred to jihad, Sweden's military presence in Afghanistan and a cartoon by a Swedish artist that depicted the Prophet Muhammad, enraging many Muslims.
It hasn't been verified that the speaker is the person who set off the explosive, but police have said they are investigating that possibility.
Police in the UK searched a property in Bedfordshire Saturday after reports that the alleged bomber lived in Luton and studied at the University of Bedfordshire, the Press Association of Britain reported. No arrests had been made and no hazardous materials were found at the property, authorities said.
Swedish Prime Minister Fredrik Reinfeldt on Sunday said the attack was 'unacceptable' but urged Swedes not to jump to "premature conclusions" that "create tension which paints pictures that are then difficult to change."
"Sweden is an open society...which has stated a wish that people should be able to have different backgrounds, believe in different in Gods...and live side by side in our open society," Reinfeldt said at a news conference.
Swedes, with a tradition of welcoming immigrants and a culture of transparency, began questioning the veracity of their self-image of being a secure nation after the 1986 murder of Prime Minister Olof Palme.
In 2003, the fatal stabbing of Foreign Minister Anna Lindh in an department store was a wake-up call for many.
But there have been no major terrorist strikes. "We had a terrorist attack in the 1970s from the Rote Armee Fraktion of Germany, but if this is a suicide bomber it is the first time in Sweden," security police spokesman Anders Thornberg told The Associated Press. "It's very serious and it's very tragic that these things have come to Sweden too."
On Sunday, the pedestrian district where the explosions occurred was eerily quiet and empty for a mid-December weekend.
German tourist Melanie Ziethmann, 34, said she heard the bang of the explosion on Saturday but didn't realize what it was until a friend in Germany contacted her to make sure she was OK. "We were surprised that this happened in Sweden," Ziethmann said. "It was quite shocking. I thought it was very safe here."
In October, Sweden raised its terror threat alert level from low to elevated because of what police called 'a shift in activities' among Swedish-based groups that could be plotting attacks.
Days later, police made several arrests over an alleged bomb plot in the country's second-largest city, Goteborg. The suspects were later released and police said the city was no longer deemed to be under threat.
Magnus Norell, a terrorism expert at the Swedish Defense Research Agency, said it was just a matter of time before Sweden was hit by a terror attack.
"Sweden isn't an isolated island, even if we might think that sometimes," he said. "We have only been lucky so far."
Norell said Sweden has the same problem with worsening radicalization among Islamic groups as other countries, with young men traveling to training camps in countries such as Somalia and Pakistan.