Nine confirmed dead in bloody attack at high school in Russian city of Kazan, 19-year-old lone shooter captured alive by police

At least nine people have died, with 16 injured, during a shooting at a school in Kazan, the capital of the Republic of Tatarstan, on Tuesday morning. The alleged perpetrator survived the incident and has been detained by police.

"We have lost seven children, eighth-grade students, four boys and three girls," Tatarstan's President Rustam Minnikhanov told the Russia-24 rolling news channel. "They died on the third floor, and 16 more people are now in hospital." The other fatality was a teacher, and the death count later rose to nine after another was subsequently recorded.

"The terrorist was arrested. He is 19-years-old... no other accomplices have been identified," Minnikhanov continued.

Students and teachers were evacuated from the building as eyewitnesses said they had heard shots and an explosion at School No. 175 in the central Russian city. Some of those inside were seen climbing from windows to escape the gunfire.

Footage emerging online purportedly taken from inside School No. 175 reveals the extent of destruction following a reported blast.

Authorities confirmed later on Tuesday that one attacker had been detained, a 19-year-old man with a registered firearm. A second was initially said to have still been engaged in a standoff with police inside the school, but officials have since said that the teenager is thought to have acted alone.

The incident occurred as Russian workplaces and institutions returned from a 10-day national holiday, marking both Labor Day and the 76th anniversary of Soviet Russia's defeat of Nazi Germany in World War II.

Kazan, located around 700km from Moscow, known as "the third capital of Russia," is a city of over 1.2 million people and the largest in the mostly Muslim region of Tatarstan.