An 11-year-old boy has died after throwing himself under a train in Japan, in an apparent suicide in protest at plans to close his school, police and press reports said Friday.

The boy, whose name was withheld, jumped onto tracks from a platform at a station in Daito, near Osaka on Thursday afternoon, police said.

"We are investigating the case as a possible suicide as eyewitnesses said the boy jumped onto the tracks by himself," a Daito police spokesman said by telephone. "There was a (suicide) note near his rucksack left on the platform."

Media reports said the child was upset about a plan to close his elementary school and send its pupils to two other institutions, part of a rationalisation made necessary by Japan's low birthrate.

"Please stop the plan to abolish and merge schools in exchange for the death of an innocent person," the suicide note read, according to the Asahi and Mainichi newspapers quoting the boy's relatives.

The boy reportedly sent a message to his mother's cell phone, saying: "Thank you for everything. I love you all very, very much."

A ceremony to mark his school's closure had been planned for Sunday but it was cancelled after his death.

The boy's death came after the December suicide of a teenager who killed himself following repeated physical abuse from his high school basketball coach in Osaka.

Japan has one of the developed world's highest suicide rates. Last year marked the first time in 15 years that the number of suicides fell below 30,000.