The victim of a deadly sword attack at a high school in central Sweden was a 17-year-old girl, police have confirmed.

Two boys aged 12 and 17 were also seriously injured in the attack at Brinell School in Fagersta on Friday afternoon, according to local authorities, while a third person sustained minor injuries.

An 18-year-old man, who has not been named, was arrested and police said they were treating the case as murder and attempted murder.

Swedish Prime Minister Ulf Kristersson and opposition leader Magdalena Andersson visited the school, where flower tributes have been laid to honour the victims, on Saturday morning.

Students at the school had only just returned to the classroom following the summer break when the deadly attack unfolded on Friday afternoon.

The police later confirmed they fired shots after being called to the scene but did not say whether the alleged attacker was hit before he was detained.

Sweden's public broadcaster reported that the suspect was wearing a helmet. Local media also said he was a former student.

The region went into a state of emergency on Friday, but it had ended by Saturday.

The school has just under 500 students on its roster, according to SVT, and is located 170km (105 miles) north-west of the capital, Stockholm.

Investigators have already carried out two house searches in connection with the suspect, police said.

On Friday, Sweden's Prime Minister Ulf Kristersson described the attack as a "serious incident," and said "we do not know what lies behind the act, but we know that police are working very intensively", in a post on X.

Sweden's King Carl XVI Gustaf said he received the news "with dismay and sadness".