What just happened in Stockholm?

Al Jazeera is reporting that a pair of explosions has rocked downtown Stockholm, Sweden.

A car exploded near Drottninggatan, a busy shopping street in the center of the city, Ulf Goranzen, a spokesman for the Swedish police, told al Jazeera on Saturday.
Shortly afterward, a second explosion was heard higher up on the same street, and a man was found injured on the ground. Goranzen said that it is still unclear what caused the blasts.
"There was series of minor explosions, causing a fire in one of the cars in the street. Some minutes later, we found a man seriously injured 300 metres away from the scene of the first explosion. This man died."

The exact cause, and whether this was intentional or accidental are both still under investigation. One cannot help but wonder if this is some kind of angry, if sloppy, lashing out against Wikileaks, which is based in Sweden, by a party affected by the recent cable disclosures.
Or perhaps Al Qaeda is making good on its vague threats to terrorize major European cities.

Fears are rising across Europe of an al-Qaeda outrage before Christmas as intelligence services work frantically to track down radicalised western nationals returning from terror camps in Pakistan.
Two scenarios are on the table; a Mumbai-style massacre using automatic weapons stored at safe houses or suicide bomb attacks using explosives also stored among radicals within the country’s massive Muslim population.

 Or maybe a car just exploded and nothing sinister is at work.