A 25-year-old attacker burst into a preschool in southern Brazil and killed four children Wednesday with a hatchet-like weapon before turning himself in to police, authorities said.

Police and government officials in the state of Santa Catarina said the man had attacked the private preschool, known as the Good Shepherd Center, Wednesday morning in the city of Blumenau, also leaving four victims wounded.

President Luiz Inacio Lula da Silva condemned the attack as a "monstrosity."

"There is no greater pain than a family that loses children or grandchildren, even more so when it is in an act of violence against innocent and defenseless children," he wrote on Twitter.

"My thoughts and prayers are with the victims' families."

A state government source confirmed to AFP the four victims were children.

Brazilian media reports said the weapon used resembled a hatchet.

Santa Catarina Governor Jorginho Mello declared three days of mourning in the state for the "terrible" attack.

Violence in schools has been increasing in Brazil in recent years.

Last week, a 13-year-old boy killed a teacher in a knife attack at a school in Sao Paulo.

In November, a 16-year-old shooter killed four people and wounded more than 10 others in twin attacks on two schools in the southeastern city of Aracruz, in Espirito Santo state.

In 2019, two former students shot dead eight people at a high school in Suzano, outside Sao Paulo, then also took their own lives.

The country's deadliest school shooting left 12 children dead in 2011, when a man opened fire at his former elementary school in the Rio de Janeiro suburb of Realengo, then killed himself.