Two blasts rocked the center of Stockholm Saturday night in what Sweden's foreign minister called "a terrorist attack" that killed one person and wounding two.
The blasts Saturday took place after Swedish news agency TT said it received a threatening letter about Sweden's military presence in Afghanistan and a years-old case of caricatures of the Prophet Mohammad.
"Now your children, daughters and sisters shall die like our brothers and sisters and children are dying," the news agency quoted the e-mail as saying.
Asked if a man found dead at the site of the second blast blew himself up in some way, police spokesman Kjell Lindgren said: "It is possible."
The incident began when a car burst into flames in the city center, followed by explosions from within the car which the police said were caused by gas canisters.
Another explosion took place, in which the man died, about 300 meters (yards) away. Two people were wounded in that blast.
"Most worrying attempt at terrorist attack in crowded part of central Stockholm. Failed - but could have been truly catastrophic," Foreign Minister Carl Bildt said in a message on Twitter, which was also shown on his blog.
Several hours after the blast, the man's body was still lying on the pavement, covered with a white sheet.
Police vans had cordoned off several streets around the body and the car had been towed away. Elsewhere, the city center was calm, with people having a normal Saturday night out.
The Swedish newspaper Dagens Nyheter quoted a man called Pascal, a trained medic, as saying, "It looked as if the man had carried something that exploded in his stomach."
"He had no injuries to the face or body in general and the shops around were not damaged."
The newspaper Aftonbladet quoted a source as saying that the man was carrying six pipe bombs, of which only one exploded.
He also had a rucksack full of nails and suspected explosive material, the newspaper said. It also quoted eyewitnesses saying the man was shouting in what was apparently Arabic.
The police declined to comment on that report.
'Stupid support for the pig'
TT said the warning, which was also sent to Sweden's Security Police, was received 10 minutes before the blasts. The agency said the mail had sound files in both Swedish and Arabic attached.
The voice on the sound file addressed Sweden and the Swedish people and talked about Sweden's silence over the caricatures of the Prophet Mohammed by artist Lars Vilks and Sweden's presence in Afghanistan, TT reported.
"Our actions will talk for themselves. As long as you do not end your war against Islam and humiliation of the prophet and your stupid support for the pig Vilks," TT quoted the man on the sound file as saying.
The man issued a call to "all the mujahedeen" in Sweden and Europe, reported The Local, Sweden's English news publication.
"Now it’s time to act, don’t wait any longer. Fear no one, don’t fear prison, don’t fear death," the email stated, according to The Local.
Holiday shoppers
Swedish media reported scenes of panic in the busy Christmas shopping areas with people fleeing amidst smoke and the smell of explosives.
Sjolander said it was unclear what caused the second explosion but a police bomb squad has been sent to the site.
Another rescue services spokesman, Roger Sverndal said the car that exploded contained gas canisters.
Gabriel Gabiro, a former AP staffer, was inside a watch store on the opposite side of the street from the second explosion and saw people running from the site.
"I saw some people crying, perhaps from the shock," he said. "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."
Gabiro said the blast was "quite loud" and he saw smoke coming from the area where the man was lying.
"It shook the store that I was in," he said of the blast. "Then there was smoke and gun powder coming into the store."
Sweden — which has so far been spared any large terrorist attacks — raised its terror threat alert level from low to elevated in October because of "a shift in activities" among Swedish-based groups that could be plotting attacks there.
The security police said then that the terrorism threat in Sweden remained low compared to that in other European countries, and no attack was imminent.
Reuters and The Associated Press contributed to this report.