HELSINKI -- One child was killed and two seriously wounded in a shooting at a school outside the Finnish capital on Tuesday, police said, with a 12-year-old fellow pupil suspected of the attack taken into custody.

The arrest of the boy was made without further violence in the Helsinki suburb of Siltamaki, 4 km (2.5 miles) south of the Viertola school in Vantaa district, police said.

Education Minister Anna-Maja Henriksson broke into tears when speaking to reporters hours after the attack in a country where gun violence among youths is rare.

"One 12-year-old child will never again return home from school," she said.

The suspect and the three victims were all sixth-graders, the police said in a statement.

"The injuries of both victims who were taken to the hospital are very serious," said Criminal Commissioner Marko Sarkka.

A national day of mourning will be observed on Wednesday, with government buildings flying the flag at half-mast, the interior ministry said.

There were no other suspects, police said. They provided no details on the identity of the suspect or victims, apart from saying they were all 12-year-old Finns and pupils at the school and the suspect was a boy.

Parents had to wait for three hours before they were able to collect their children, with lots of tears and hugs when they were reunited outside the police barricade. Children had to leave their coats behind.

Prime Minister Petteri Orpo said the shooting was deeply shocking. He encouraged parents to comfort their children and help alleviate any fears about further such attacks.

"I want to tell children and young people all over Finland that the Finnish authorities and school staff are doing everything they can every day to prevent something like this from happening," Orpo said in a statement.

The suspect had admitted the attack in a preliminary interview, police said, and the offences would be investigated as murder and attempted murder.

No one has yet spoken on the suspect's behalf. He will be put in the care of social services because a child cannot be remanded in custody, police said.

Police said the motive was not clear. The handgun's permit belonged to a relative of the suspect, they said.

Video circulating on social media and unverified by Reuters showed two police kneeling at the side of the suspected shooter who was lying face down on a sidewalk.

The Viertola school has around 800 pupils from first to ninth grade and a staff of 90, according to the municipality.

Anja Hietamies, the mother of an 11-year-old pupil, told Reuters she received a message from her scared daughter after the shooting.

"She said they were in a dark, locked classroom, not allowed to speak on the phone but could send messages," Hietamies said.

Interior Minister Mari Rantanen said on X: "The day started in a horrifying way...I can only imagine the pain and worry that many families are experiencing at the moment. The suspected perpetrator has been caught."

Previous school shootings in Finland have put a focus on Finland's gun policy.

In 2007, student Pekka-Eric Auvinen shot and killed six students, the school nurse, the principal, and himself using a handgun at Jokela High School, near Helsinki.

A year later, in 2008, Matti Saari, another student, opened fire at a vocational school in Kauhajoki in northwest Finland. He killed nine students and one male staff member before turning the gun on himself.

Finland tightened its gun legislation in 2010, introducing an aptitude test for all firearms licence applicants. The minimum age for applicants was also raised to 20 from 18.

It was too early to draw any policy conclusions from Tuesday's attack, Rantanen told a press conference.

There are more than 1.5 million licensed firearms and about 430,000 licence holders in the nation of 5.6 million people, where hunting and target shooting are popular.