A teenage boy injured six people, five of them minors, in an axe attack in a Siberian classroom on Friday, local authorities said, days after 15 were injured in a knife fight at another Russian school.
Investigators said the boy, thought to be 15 or 16, carried out the attack in a class of children aged around 12 or 13 in the city of Ulan-Ude near the Mongolian border.
He also set the classroom on fire with a bottle of fuel, before jumping out of the window.
"As a result of his actions, five pupils and a teacher were wounded," the Investigative Committee, which probes major crimes, said in a statement.
"It has been established that the attacker acted alone. He was detained and is currently in hospital after he attempted to kill himself," a local representative of the Investigative Committee told TASS news agency.
Doctors in Ulan-Ude told RIA Novosti agency that an 11-year-old girl is in "a very serious condition" after suffering a head injury and another girl had two fingers amputated.
Video footage released by investigators showed charred walls and burnt books strewn across the classroom floor.
Investigators said they were checking the school's security system. They have launched criminal cases over attempted murder and negligence.
The incident came as two teenagers have been charged with attempted murder after 15 people including themselves were injured in a mass knife fight on Monday in a school in Perm, a city in the Urals.
Russian authorities on Friday said they would check for any links between the Buryatia and Perm incidents.
The education ministry and Russian children's rights commissioner sent delegations to Buryatia following the attack.
The attacks have reignited a debate over security in schools and the influence of social media on teenagers, with fears centring on groups that urge young people to commit suicide.
The vice speaker in Russia's lower house of parliament Irina Yarovaya called for school children to have lessons on how to use social media safely, TASS reported.
Deputy mass communications minister Alexei Volin said he had received assurances from the country's communications watchdog that social media groups calling for violence in schools will be blocked.
"We already reached a deal with Roskomnadzor that those groups will be blocked," Volin told Interfax news agency.