Two explosions in central Stockholm have killed one person and injured two, causing panic among Christmas shoppers.

A car exploded near Drottninggatan, a busy shopping street in the centre of the city.

Shortly afterward, a second explosion was heard higher up on the same street, and a man was found injured on the ground. He was later pronounced dead.

Two other people were taken to the hospital, but it was not immediately clear in which explosion they were hurt.

Rescue services spokesman Roger Sverndal said the car that exploded contained gas canisters.

Sjolander said it was unclear what caused the second explosion and if the two blasts were linked, but said a police bomb squad has been sent to the site.

Sweden - which has so far been spared of any large attacks - raised its security 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 that the extremist threat remained low compared to that in other European countries, and no attack was imminent.