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.

Witnesses who survived Sweden’s worst mass shooting have described horror and panic that gripped an adult education center west of Stockholm as the gunman killed at least 10 people.

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

A gunman who killed 11 people, including himself, at an adult education centre in central Sweden may have been a student at the school, police said on Thursday, as they described chaotic scenes after the country's deadliest mass shooting as being like an "inferno".

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

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.

The victims of Sweden's worst mass shooting were seven women and three men aged between 28 and 68, police said on Friday after completing the identification process. They were killed at an adult education centre in the city of Orebro on Tuesday, about 125 miles (200km) from Stockholm, in an attack that has sent shockwaves through Sweden.

Rickard Andersson, aged 35 has been identified as the shooter in the Sweden Örebro school massacre, a reclusive loner who turned the gun on himself.