Swedish police said Sunday the two explosions that hit central Stockholm on Saturday night were "terror attacks" committed by what appeared to be a suicide bomber who killed himself and injured two people.

"What had happened was really very serious," Security Police official Anders Thornberg said.

He said the police did receive an e-mail complaining that they were not satisfied with Swedish troops' presence in Afghanistan.

The first explosion occurred in a car parked near the Queens street, one of the busiest shopping streets in the city, and the second on another street about 200 meters away just minutes later. A man who burnt himself was found dead near the site of the second blast.

Police had begun an investigation into the explosions. But they did not directly confirm if the dead man had any relation with the exploded car.

"We will do whatever we can to investigate the matter, but it is still under the investigation," Thornberg added.

Swedish Foreign Minister Carl Bildt said in his twitter after the explosions that he was very concerned about the incident and warned of catastrophic consequences.