A sports plane crashed on Sunday near the university town of Umea in the northern Swedish province of Vasterbotten, killing all nine people on board, including the pilot.

All eight of the passengers were parachute jumpers, Sweden's national association of parachutists confirmed in a statement.

The Swedish Accident Investigation Authority said it would launch an investigation but warned that the fact-finding mission and analysis "will most likely continue for quite some time." There was no black box on board the plane.

The accident is the most serious in 30 years in Sweden.

Indications are that it took place shortly after take-off at an airport in Umea and crashed on Storsandskar island, about 2km south of the airport.

Videos from witnesses showed the plane's nose hitting the ground at high velocity. A witness told the Aftonbladet newspaper he heard a loud boom after the crash, after which everything went quiet.

King Carl XVI Gustaf spoke to the victims' loved ones and offered his condolences, as did Swedish Prime Minister Stefan Lofven.

"The government is in close contact with the relevant authorities, and it is now important to investigate the cause of the crash," Lofven said in a statement.

Umea is a city of around 80,000 people, about 500km north of Stockholm.

Australian Associated Press