Eighteen people were killed and dozens injured Wednesday at the college in Crimea when at least one attacker set off a bomb in the cafeteria and went through the building shooting at random, officials said.
Sergei Aksyonov, Crimea's Russian-backed leader, was quoted by the Interfax news as saying an 18-year-old male student was a suspect and that he had since committed suicide.
Video footage showed armoured personnel carriers and military tucks lined up near the college in the Crimean city of Kerch.
A local resident said officials had instructed parents to pick up their children from schools and kindergartens for their safety.
Olga Grebennikova, the college's director, told Crimean media outlets in an interview outside the college that the bodies of children were everywhere.
The investigative committee, the law enforcement body that investigates major crimes, said initial information was that an explosive device packed with metal objects had gone off in the cafeteria of the college.
About 50 people, many of them teenagers, were wounded in the attack, the committee said.
2014 Russian invasion
Russia annexed the Black Sea peninsula of Crimea from Ukraine four years ago, prompting international condemnation and Western sanctions.
An employee at a hospital in Kerch was quoted as saying that 18 people had already been admitted with injuries from the explosion and doctors were expecting around 50 more wounded people to be brought in.
"There are already lots of people in the emergency room, and in the operating theatre," TASS news agency quoted the employee as saying.
Photographs from the scene of the blast posted by local media outlet Kerch.FM showed the ground-floor windows of the two-storey building had been blown out and debris lying on the floor outside.