Fifteen people have been injured in Russia after two teenagers inspired by the Columbine massacre stabbed younger children and a teacher.

The teacher and the two attackers aged 15 and 16 were in critical condition on Monday in Perm, a city of a million people near the Ural Mountains, according to the governor's office.

Footage from the scene showed police leading a bloodied, shirtless teenager away from the school in handcuffs, as well as blood splattered across the floor of a classroom.

Russia's investigative committee said the bloodshed had occurred when the teacher and her pupils tried to break up a knife fight between a current student and his former classmate.

Other accounts, however, said the incident began as an attack on the school. The regional children's ombudswoman told Perm news site 59.ru that security had failed to catch the two teenagers, who climbed to a fourth-grade class on the third floor with knives. At that point, a fight broke out between the two attackers, and the teacher and students “were drawn into the conflict,” she said.