Russian officials say a teenager armed with an ax has attacked fellow students at a school in southern Siberia, wounding five children and their teacher.

Russia's Investigative Committee said the ninth-grader entered a class during a lesson Friday and attacked seventh-graders and their teacher. He ignited a firebomb in the class and tried to kill himself before being apprehended.

The attacker has been hospitalized and an official probe has been launched. His motives weren't immediately clear.

The attack happened in Sosnovy Bor on the outskirts of Ulan-Ude, the regional capital of Buryatia, a region near the Russia-Mongolia border.

It's the second attack on a school this week. Two teenagers stabbed children and their teacher with knives Monday, wounding 15 people, and then attempted to kill each other but were detained.