A gunman has attacked a school in the Russian city of Kazan, killing eight people – seven students and a teacher – and leaving 21 other people in hospital, officials said.

Rustam Minnikhanov, governor of the Tatarstan republic where Kazan is the capital, said four male and three female eighth-grade students died in the shooting.

His press service later added that a teacher was also killed.

“The terrorist has been arrested, (he is) 19 years old. A firearm is registered in his name. Other accomplices haven’t been established, an investigation is under way,” Mr Minnikhanov said after visiting the school, adding that security had been restored there.

According to Tatarstan health officials, 21 people were taken to hospital with wounds after the attack, including 18 children, six of them in intensive care.

Russia’s state RIA Novosti news agency reported earlier that 11 people had been killed in the Kazan school shooting. There was no way to immediately reconcile the differing death tolls.

Authorities said additional security measures were put in place at all schools in Kazan, a city 700 kilometres (430 miles) east of Moscow.

Police opened a criminal investigation into the shooting.

Footage of the school building showed dozens of ambulances lined up in front of the entrance.

While school shootings are relatively rare in Russia, there have been several violent attacks on schools in recent years, mostly carried out by students.