MOSCOW: Nine people, including seven children, were killed on Tuesday and many more badly wounded after a lone teenage gunman opened fire in a school in the Russian city of Kazan, local authorities said, prompting a Kremlin call for tighter gun controls.

Two children could be seen leaping from the third floor of the four-storey School Number 175 to escape as gunshots rang out, in a video filmed by an onlooker that was circulated by Russia's RIA news agency.

"We heard the sounds of explosions at the beginning of the second lesson. All the teachers locked the children in the classrooms. The shooting was on the third floor," said one teacher, quoted by Tatar Inform, a local media outlet.

Calling the attack a tragedy for the country, Rustam Minnikhanov, the head of the wider Tatarstan region, said there was no evidence that anyone else had been involved.

"We have lost seven children - four boys and three girls. We also lost a teacher. And we lost one more female staff worker," he said in a video address.

"The terrorist has been arrested. He's a 19-year-old who was officially registered as a gun owner," he said. He said the victims were in the eighth year of school, which in Russia would make them around 14 or 15 years old.

Russia's Investigative Committee, which investigates major crimes, said in a statement it had opened a criminal case into the shooting and that the identity of the detained attacker had been established.

Reuters could not immediately contact a lawyer for the suspect, who was named in Russian media but whose identity was not officially disclosed, standard practice in Russia until a suspect has been formally charged.

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