Twenty people were killed by a gunman at a college in the Black Sea region of Crimea who set off a bomb in the cafeteria and went through the building shooting anyone he saw.

Law enforcement officials said they were treating the incident as a terror attack. Video footage from the scene showed armored personnel carriers and military trucks lined up on the approach to the college, in the Crimean city of Kerch.

A local resident said officials had instructed parents to collect their children from schools and kindergartens in the city 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.