One person has been killed and two others hurt by two blasts in the centre of the Swedish capital, Stockholm, amid reports of a bomb attack.
A car blew up near the busy shopping street of Drottninggatan and another blast followed nearby minutes later.
Swedish press reported that the second blast was a suicide bomber, but police said no cause had yet been determined.
Foreign Minister Carl Bildt said a "terrorist attack" which could have been "truly catastrophic" had failed.
Tweeting about the blasts, he described them as "most worrying".
A local news agency, TT, said it had received a threatening e-mail shortly before the blasts, which called for "mujahideen", or Islamist fighters, to rise up in Sweden and Europe.
Attacking the country over caricatures of the Prophet Mohammed drawn by Swedish artist Lars Vilks as well as Sweden's military presence in Afghanistan, the e-mail promised Swedes would "die like our brothers and sisters".
Sweden has some 500 soldiers deployed in Afghanistan as part of the international military force.
In November, Sweden raised its terror alert level from low to elevated because of a "shift in activities" among Swedish-based groups thought to be plotting attacks.
The two blasts both hit central Stockholm as the city's streets were busy with people out Christmas shopping.
The car exploded at 1700 (1600 GMT) on Saturday and the second blast occurred 10 to 15 minutes later on a street about 300m (300yds) away, police spokesman Kjell Lindgren said.
A man was found dead near the site of the second explosion. Two people with minor injuries were also found nearby.
Asked if the dead man had somehow blown himself up, Mr Lindgren said: "It is possible."
Unconfirmed reports in Sweden's Aftonbladet newspaper said the man was carrying pipe bombs, as well as a backpack full of nails.
Another police spokesman, Ulf Johansson, told the BBC police would not rush to judgement.
"We need more investigation and of course we need more witnesses to give us the information of what actually has happened," he said.
He said the car had contained gas canisters and had "exploded with a series of minor explosions".
The identities of the dead man and those injured have not been released.
A former employee of the Associated Press news agency, Gabriel Gabiro, was close to the second blast.
"I saw some people crying, perhaps from the shock," he told the agency.
"There was a man lying on the ground with blood coming out in the area of his belly, and with his personal belongings scattered around him."
A trained medic named only as Pascal also said the man appeared to have a stomach injury.
"It looked as if the man had carried something that exploded in his stomach," he said on the website of newspaper Dagens Nyheter.
"He had no injuries to the face or body in general and the shops around were not damaged."