At least 19 people have been killed and dozens more wounded in a shooting at a college in Russian-annexed Crimea.

An 18-year-old student ran through the technical college in Kerch firing at fellow pupils before killing himself, Russian investigators say.

Witnesses have also spoken of at least one blast caused by an unidentified explosive device before the shooting.

Russia seized Crimea from Ukraine in 2014 in a move condemned by many Western powers.

The annexation marked the start of a simmering conflict involving Russian-backed rebels in eastern Ukraine that goes on to this day.

Details are still emerging, and there are contradictory reports about the chronology of the attack.

The alleged perpetrator, named Vladislav Roslyakov, is said to have run from room to room as he fired, starting in the area near the canteen. He then shot himself dead, Russia's investigative committee said.

Photos later emerged in Russian media purportedly showing the body of the attacker in the college library.

The investigative committee said initial examinations suggested all the victims died of gunshot wounds, but some reports speak of shrapnel injuries.

At the same time, Russia's law enforcement sources are quoted by local media as saying that the attacker had detonated a bomb in the canteen before starting shooting.

Soon after reports of a blast in the college, investigators released a statement saying an explosive device filled with "metal objects" had detonated in the dining area.

Several witnesses maintain they heard one or more explosions.

Investigators later said they found a second device among the personal possessions of the gunman and that it had been disarmed.

BBC Russian has been speaking to witnesses, including Igor Zakharevsky, who was in the canteen when the gunman struck.

"I was at the epicentre of the first explosion, at the entrance, near the buffet," he said.

"I was in complete shock and one of my classmates started pulling me away. Then I heard several shots at intervals of two or three seconds. After a while there was another explosion."

National guard soldiers were deployed and schools and pre-schools in the city were evacuated.

A businessman near the college described hearing an explosion and seeing a large window shatter. (BBC)

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