Officials in Sweden have vowed to determine why a man killed 10 people, and apparently himself, in an unprecedented attack that's shaken their "society to its core."

All Swedish schools and pre-schools will have to make plans to keep unauthorised people off their premises, the government said on Wednesday, as the country tries to come to terms with the worst school shooting in its history last week.

Swedish police say about 10 people have been killed in a shooting at a school for adults in the city of Orebro, including the suspected gunman.

Sweden’s prime minister said the attack at the Risbergska School was the worst mass shooting in country’s history

One day after the killings at an adult educational center, some gathered to lay flowers and come to grips with the violence.

Sweden’s right-wing government said on Friday it would seek to tighten gun laws in the wake of the country’s deadliest mass shooting at an adult education center where the attacker appeared to have used several of his own licensed rifles.

The gunman was among the 11 people killed in the worst shooting in the history of Sweden at an adult education centre west of Stockholm. On Tuesday, police received reports of a shooting in Orebro, a city 200km (124 miles) west of Stockholm, at 12.33pm local time and engaged in an exchange of bullets with the suspect.

A mass shooting incident at the Risbergska school in Orebro, central Sweden, left at least five people wounded, with the suspected shooter reportedly among the injured. The shooting occurred around 12:30 p.m. local time, prompting an immediate police response.