At least nine people have been killed, including seven children, and many more wounded after a gunman, reported to be a 19-year old former student, opened fire at a school in the south-western Russian city of Kazan.

Two children could be seen leaping from the third floor of the four-storey School Number 175 as gunshots sounded, in a video filmed by an onlooker and circulated by news agency RIA.

Four boys and three girls, all eighth-graders, died as well as a teacher and another school employee, Tatarstan Republic governor Rustam Minnikhanov said. Of the 21 wounded and hospitalised, six are in extremely grave condition, authorities said.

The attacker, identified only as a 19-year-old, was arrested, officials said.

They gave no immediate details on a motive.

“The terrorist has been arrested, 19 years old. A firearm is registered in his name. Other accomplices haven’t been established. An investigation is underway,” Mr Minnikhanov said.

But Russian media said the gunman was a former student at the school who called himself “a god” on his account on the messaging app Telegram and promised to “kill a large amount of biomass” on the morning of the shooting.

https://twitter.com/disclosetv/status/1392024339994845185

Footage posted on social media showed a young man being pinned to the ground outside the school building by a police officer.

Children seen jumping from building amid school shooting in Kazan, Russia; at least 9 killed pic.twitter.com/c8vlJcq4zV

— BNO News (@BNONews) May 11, 2021

School shootings are rare in Russia. One of the last major incidents took place in Russian-annexed Crimea in 2018 when a student at a college killed 19 before turning his gun on himself.

Kazan is the capital of the Muslim-majority region of Tatarstan and located around 800 kilometres east of Russia’s capital, Moscow.

Russian officials promised to pay families 1 million roubles ($A17,210) each and give 200,000 to 400,000 roubles to the wounded.

-AAP