A gunman shot and killed a police officer and a teacher, and held more than 20 students hostage at a school on the outskirts of Moscow.

The armed attacker was carrying a rifle as he forced his way into the premises this morning and took hostage the ninth grade pupils - all aged around 15 years old - along with a teacher in a biology class.

The teenage gunman is said by authorities to be a student at the number 263 high school, situated in the northwest of the Russian capital.

A guard, who was injured in the assault, managed to raise the alarm by triggering an emergency button and police immediately responded.

Scores of officers and ambulances arrived at the scene and were fired at by the gunman through a school window.

One officer who had been shot died at the scene.

The gunman was arrested and the hostages freed from the premises, outside of which friends and family had gathered to await news about their loved ones.

Interior Ministry spokesman Andrei Pilipchuck told state TV: "The person who took 20 people and a teacher hostage is a student in the upper classes at the same school.

"He has been neutralised and all the students have been freed.

"One policeman was fatally wounded during the operation and died in hospital, and a teacher at School No 263 was also killed."