At least 18 people reportedly were killed due to gas explosion took place in a technical school in Crimea's Kerch city, while 50 others were injured.
Spokesman of the Russian Investigation Committee Svetlana Petrenko stated that the number of deaths increased to 13 first, and the number of wounded people increased to 50, while 3 of the serious casualties lost their lives, thus increasing the number of deaths to 18.
Eyewitnesses said the explosion might have been caused by a gas leak in the school's canteen.
One source among the Kerch security forces also said the explosion occurred in the canteen and that the gas explosion was considered as the first possibility, but the cause was not known.
"Unknown explosives used"
Officials from the Russian National Counter-Terrorism Committee reported that an unknown explosive device used in the blast.
Russian President Vladimir Putin has been informed about the incident, Kremlin said. Russia's Investigative Committee has launched an investigation into the incident.
Meanwhile, the local press claimed that the gunshots had been heard before the explosion.
The Kremlin spokesman Dmitriy Peskov said they were concerned about the possibility that the incident was a "terrorist attack."
Russian National Guard (Rosgvardiya) Deputy Chairman Sergey Melikov told reporters that a hand-crafted explosive was used in the incident.
Two eyewitnesses spoke to Russia Today (RT) told reporters that gunshots were heard during the blast, masked and armed men running around the building killed students.
One student said that the masked men were running with rifles in their hands after the explosion.
"There were a lot of masked men. I don't know how many they were. The students, the teachers, they shot everyone in front of them. I think they shot a lot of people. And they were throwing explosives around," another student said. (ILKHA)