Two blasts rocked the centre of Stockholm on Saturday in a possible attack inspired by Sweden's presence in Afghanistan, killing the bomber and wounding two other people.
A Swedish news agency said that 10 minutes before the first blast it received an email with threats over the Swedish presence in Afghanistan and over a case of caricatures of the Prophet Mohammad by a Swedish artist in 2007.
The BBC reports that Foreign Minister Carl Bildt said a "terrorist attack" which could have been "truly catastrophic" had failed.
Police spokesman Kjell Lindgren said the car exploded at peak shopping hours at 5pm local time.
About 10 to 15 minutes later another explosion took place on a street 300 metres away.
A man was found dead near the second explosion and two people with minor injuries were also found nearby.
Asked if the man blew himself up in some way, Mr Lindgren said: "It is possible."
Investigations were continuing to see if the two incidents were linked, he said.
He said a bag found near the dead man had also been examined, but no more explosives were found in it.
One newspaper quoted a source as saying that the man was carrying six pipebombs, of which only one exploded.
He also had a rucksack full of nails and suspected explosive material, the newspaper said.