Swedish authorities have confirmed 11 people have died in a school shooting, marking the country’s deadliest gun attack in what the prime minister called a “painful day.”

Police said the gunman was believed to be among those killed as a search for further victims continued at the school, located in the city of Orebro.

The gunman’s motive remains a mystery.

“We know that 10 or so people have been killed here today. The reason that we can’t be more exact currently is that the extent of the incident is so large,” local police chief Roberto Eid Forest said.

Later the police website said: “At this time, there are 11 deaths due to the incident. The number of injured is still unclear. We currently have no information on the condition of those who have been injured.”

Police earlier warned the death toll could rise further. Several of those injured were in hospital, including at least four in surgery.

Orebro University Hospital said it was treating five people with gunshot wounds and a sixth with “minor injuries” from another cause. No children were among the injured.

Forest said police believed the gunman had acted alone and that terrorism was not suspected as a motive, though he cautioned that much remained unknown. He said the suspected gunman was previously been known to police.

“We have a big crime scene, we have to complete the searches we are conducting in the school. There are a number of investigative steps we are taking: a profile of the perpetrator, witness interviews,” Forest said.

The shooting was in Orebro, 200 kilometres west of Stockholm, at a school in the suburb of Risbergska.

It caters to adults who did not complete their formal education or failed to get the grades to continue to higher education, and shares its campus with schools for children.

Police said they were still examining the crime scene and had searched addresses in Orebro after the attack.

Late on Tuesday (local time), police vans and personnel were still outside an apartment building in central Orebro that had been raided earlier.

Prime Minister Ulf Kristersson said it was the worst mass shooting in Swedish history.

“It is hard to take in the full extent of what has happened today – the darkness that now lowers itself across Sweden tonight,” he said.

King Carl XVI Gustav conveyed his condolences. “It is with deep sadness and dismay that my family and I received the news about the terrible atrocity in Orebro,” he said.

European Commission President Ursula von der Leyen expressed her sympathy on X, saying: “In this dark hour, we stand with the people of Sweden.”

One of the school’s teachers, Maria Pegado, said someone threw open the door to her classroom just after lunch break and shouted to everyone to get out.

“I took all my 15 students out into the hallway and we started running,” the 54-year-old told Reuters.

“Then I heard two shots but we made it out. We were close to the school entrance.

“I saw people dragging injured out, first one, then another. I realised it was very serious.”

Another witness, a student who gave only her first name, Marwa, said she and several others had tried to save one person’s life.

“A guy next to me was shot in the shoulder. He was bleeding a lot. When I looked behind me I saw three people on the floor bleeding,” she told TV4 Sweden.

She and a friend wrapped a shawl around the injured man’s should “so that he wouldn’t bleed so much”.

Many students in Sweden’s adult school system are immigrants seeking to improve basic education and gain degrees to help them find jobs in the Nordic country while also learning Swedish.

Sweden has struggled with a wave of shootings and bombings caused by an endemic gang crime problem that has driven the rate of gun violence in the nation of 10 million people to the highest in the EU in recent years.

Sweden has a high level of gun ownership by European standards, mainly linked to hunting, though it is much lower than in the US. The gang crime wave has highlighted the high incidence of illegal weapons.

-with AAP