One person has been killed and two others injured as two explosions rocked the centre of the Swedish capital, Stockholm, police say.
A car blew up near the busy shopping street of Drottninggatan, and another explosion hit nearby minutes later.
Swedish press attributed the second blast to 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 on the blasts, he described them as "most worrying".
A local news agency, TT, said it had received an e-mail shortly before the blasts, which said it was now time for Swedish people to die "like our brothers and sisters".
Mats Johansson said the message was addressed to Sweden and the Swedish people.
It included references to caricatures of the Prophet Mohammed drawn by Swedish artist Lars Vilks as well as Sweden's military presence in Afghanistan, Mr Johansson said.
Sweden has 500 soldiers deployed in the country as part of the international peacekeeping force.
Police probe
Both blasts hit central Stockholm as the streets were busy with people out Christmas shopping.
A man's body was discovered after the second blast.
Unconfirmed reports in Sweden's Aftonbladet newspaper said the man was carrying pipe bombs, as well as a backpack full of nails.
But 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. "The car exploded with a series of minor explosions and there was also some kind of explosion close up to where we found the dead man," he said.
He said there had been no warning of any attacks and confirmed that two people were lightly injured.
Another police spokesperson said it was unclear if the two blasts were linked.
The identities of the victims 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."
