The mother of a 13-year-old boy who killed himself in eastern France this month said Monday she believed homophobic bullying by classmates had "triggered" his suicide.

"For me, the bullying was the element that triggered it," the 35-year-old mother who identified herself only as Severine told reporters in Epinal.

Her son Lucas hanged himself in early January, with prosecutors saying he had been bullied at school "for several months due to his homosexuality".

Four 13-year-old children at the middle school now face trial for instigating the boy's suicide through bullying, regional prosecutor Frederic Nahon said Friday.

Lucas' mother Severine said Monday that "they're still just children" and should be "protected", after threats were published against the accused on social media.

"Of course I hold it against them, my son is no longer with us" because they "were mean to him", she added in a voice choked by tears.

Severine said she hoped the court appearance would make the suspected bullies "think" and "lead them to act", saying she herself planned to appear in schools to warn against harassment.

"They should come with us, it might be good for them to join in" to explain the consequences of their actions, she added.

Prosecutors said Friday the other children had "only admitted making fun of their classmate several times" rather than systematic bullying.

But people close to Lucas, who wrote a note explaining his wish to take his own life in his diary, say he had suffered homophobic mockery and insults at school in the town of Golbey.

The four classmates -- two boys and two girls who were detained for questioning and then released -- will be tried by a special court for children.

A second investigation against persons unknown is underway for failing to report mistreatment of a minor.