German state prosecutors have charged a 17-year-old with four counts of attempted murder as well as grievous bodily harm after a knife attack at a high school in the western German city of Wuppertal in February.

On February 22, four male students suffered stab wounds after the 17-year-old suddenly attacked his fellow pupils during a break between lessons before causing severe injury to himself as well.

There were no fatalities but three of the pupils, including the attacker, were treated in intensive care, while three further female students suffered from shock.

Following initial investigations at the end of February, prosecutors said a teacher had been made aware of the attack after hearing shouts.

They said the teacher had managed to calm the attacker down and disarm him, but that he still attempted to attack armed police officers who arrived on the scene in response to an emergency call from the school secretary's office.

A possible motive for the attack was not clear. However, a letter found at the scene led investigators to suspect mental illness.

The 17-year-old was remanded in custody, a remand which state prosecutors have also requested be extended.

The youth court in Wuppertal will decide when to open proceedings against the minor.

mf/wmr (AFP, dpa)