The motives and causes of the blast at Crimea’s Kerch college will be thoroughly investigated and the results of this effort will be reported to the public, Russian President Vladimir Putin told reporters on Wednesday.

"The motives and theories of this tragedy are thoroughly investigated," Putin said. "The public will be informed about the results of this effort by the law enforcement agencies and special services," he said. "Now it is clear that this is a crime."

"Several hours ago a tragic event occurred in Russia, in the city of Kerch. People died and many are wounded after an explosive device went off," the president said. Putin offered condolences to the relatives of victims and wished a speedy recovery to those injured. "We will make every effort for that," he said.

Earlier on Wednesday, 18 people were killed and another 47 were wounded at the Kerch technical college when a senior who was attending that college went on a shooting spree. Six people are in critical condition, the emergency medicine center said. The shooter committed suicide.

The criminal case was initially opened into a terrorist attack, but later a criminal investigation into murder was launched.