Three people were killed when a bus carrying around 50 school children and a few adults rolled over on a road in northern Sweden on Sunday, news agency TT said.

Police said it was unclear what had caused the accident.

Around 28 people were injured, according to daily Expressen.

"We know they drove off the road. We don't know much more than that at this point," police spokeswoman Marie Andersson said.

The accident occurred close to the town of Sveg in the northern region of Harjedalen.