Finnish police officer stands alert. Picture used for illustrative purposes only.

A child opened fire on Tuesday at a primary school in Vantaa outside the Finnish capital Helsinki injuring three others, police said, adding that the attacker was in custody.

"All those involved in the shooting incident are minors. According to the police's current information, there are three injured," a police statement said.

The shooting took place at the Viertola school in Vantaa, a suburb to the capital Helsinki, which has around 800 students from first to ninth grade and a staff of some 90 people, according to the local municipality.

"The immediate danger is over," the Viertola school's principal Sari Laasila told Reuters, declining to comment further on the incident.

Agencies