The student gunman who killed at least 19 people and injured dozens more at a college in the Black Sea region of Crimea appeared to dress and use a gun similar to Columbine killer Eric Harris.

Eighteen-year-old Vladislav Roslyakov turned up at the college in the city of Kerch yesterday afternoon carrying a firearm and began shooting, investigators said.

His body was later found in the college with what they said were self-inflicted gunshot wounds.

There were no immediate clues as to his motive in mounting such an attack, which recalled similar shooting sprees carried out by students in US schools.

Despite that, images of Roslyakov released through local media outlets appear to show the teenager dressed in a white t-shirt, black pants and brandishing a shotgun.

The appearance is a near-mirror image of 18-year-old Harris, who helped kill 13 people and wound 24 others at Columbine High School in Columbine, Colorado on April 20, 1999 in one of the United States' worst-ever school shootings.

Russian officials at first reported a gas explosion, then said an explosive device ripped through the college canteen at lunchtime in a suspected terrorist attack.

At least 19 people have been killed after an explosive device detonated at a college in Crimea. (AAP/Kerch fm)

Russian officials said it may have been a terror attack. (AAP/Kerch fm)

Russia annexed Crimea from Ukraine in 2014, prompting international condemnation and Western sanctions, but since then there have been no major outbreaks of violence there.

Many of the victims from yesterday's attack were teenage students who suffered shrapnel and bullet wounds.

Pupils and staff described scenes of mayhem as panicked pupils tried to flee the building. They said the attack had started with an explosion, followed by more blasts, and a hail of gunfire.

An army tank is seen at the scene of an attack on a school in Kerch in Crimea, Russia. (AAP)

Military forces block the road to the site of attack at a vocational school in Kerch in Crimea, Russia. (AAP)

Military and police near the site of an attack at a vocational school in Crimea, Russia. (AAP)

Russian President Vladimir Putin declared a moment's silence for the victims.

"This is a clearly a crime," he said. "The motives will be carefully investigated."

Olga Grebennikova, the college's director, told Crimean media outlets in an interview outside the college that the bodies of children were everywhere.

Local people gather near a school where a bomb is believed to have been detonated in Crimea, Russia. (AAP)

Troops with armoured personnel carriers were sent to the scene. Local parents were told to collect their children from the city's schools and kindergartens for their safety.

However, the Investigative Committee, the state body that investigates major crimes, said later that it was re-classifying the case from terrorism to mass murder.

An employee at Kerch's hospital said dozens of people were being treated for their injuries in the emergency room and in the operating theatre.

Tributes have started flowing in from local residents and students, for those who were killed in the attack. (AAP)

Mourners were seen laying flowers at a monument to the city of Kerch. (AAP)

The incident has sparked an outpouring of emotion from people living in the city. (AAP)

Photographs from the scene of the blast showed that the ground floor windows of the two-storey building had been blown out, and that debris was lying on the floor outside.

Emergency services teams have been carrying wounded people from the building on makeshift stretchers and loading them on to buses and ambulances.