The French government on Thursday launched an urgent investigation after a 14-year-old girl was severely wounded and left in a coma after being beaten outside her school by three other teenagers in the south of France.

The three alleged attackers, including a girl who was at the same school as the victim in the suburbs of the southern city of Montpellier, have been arrested on suspicion of attempted murder of a minor.

The incident comes at a time of heightened tensions around French schools after dozens of messages threatening attacks were sent through an internal messaging system.

The victim, named as Samara, has now come out of her coma but was "seriously wounded" in the attack on Tuesday afternoon outside the Arthur Rimbaud college in the La Mosson-La Paillade district, a low-income suburb with many residents of immigrant origin, prosectors said.

One of the accused is a girl from the same school, also 14, who was arrested on Wednesday and admits to having beaten the victim, Montpellier prosecutors said in a statement late on Wednesday.

The two other minors arrested are aged 14 and 15.

Education Minister Nicole Belloubet ordered an investigation by inspectors from her ministry who would have eight working days starting from Friday to report back on the circumstances surrounding the attack.

"This mission will aim both to establish the reality of the facts and to establish responsibilities," she told BFMTV, adding that Samara was owed "the truth".

Her mother, Hassiba, has said in media interviews that her daughter had been bullied by a fellow pupil for two-and-a-half years, raising the possibility this could have been over her behaviour and clothing being deemed un-Islamic.

"I don't actually understand this child's reasons for constantly attacking Samara, but there is something. I think it's... the fact that she (Samara)... is maybe a little more liberated than some students," she told BFMTV.

She accused this classmate of being the "sponsor" of the attack and claimed that this schoolgirl had been suspended for two days in June 2023, in particular after having published a photo of her daughter on social networks calling for her to be raped.

President Emmanuel Macron in televised comments expressed "solidarity" with the girl but urged caution in drawing conclusions about the circumstances of the attack.

"At this stage I would be weary of categorising things and I want the full truth to be established in calm and the conclusions to be drawn then," he said.