A 15-year-old student has been arrested on suspicion of murdering a 14-year-old classmate at a secondary school near Dortmund, German police said.

The fatal attack – reported to be a stabbing – occurred at the Käthe Kollwitz comprehensive school at around 8am local time in the town of Lünen.

Bild reports the 15-year-old was spotted by a police helicopter fleeing the scene. He was arrested nearby and is in custody.

According to local media, both are German citizens, though the suspect reportedly has a Kazakh passport.

Lünen Mayor Jürgen Kleine-Frauns issued a statement confirming the death, adding: “This terrible act deeply affects me. We are all horrified and stunned. Our deep compassion and concern are for the family of the victim. But our thoughts are also directed at the school community. In these difficult hours we are there for you.

“There are no words that can give comfort. But we will show that we stand together in such situations in Lunen. So we will meet tomorrow, Wednesday at 12 o’clock to a minute of silence.”