Officials in Crimea say an 18-year-old student is responsible for carrying out an attack on his college in the city of Kerch that killed at least 19 people.

Key points: Officials said a 18-year-old male student was behind the attack

Officials said a 18-year-old male student was behind the attack An explosive device full of metal objects was set off in the cafeteria

An explosive device full of metal objects was set off in the cafeteria Russia annexed Crimea from Ukraine four years ago

The gunman, Vladislav Roslyakov, burst into Kerch Polytechnic College in the Black Sea region of Crimea, set off a bomb in the cafeteria, and went through the building shooting anyone he saw, officials and the college's director said.

Roslyakov, turned up at the college in the city of Kerch on Wednesday afternoon carrying a firearm and then began shooting, investigators said.

The body of the fourth-year student was later found in the college's library with what they said were self-inflicted gunshot wounds.

Russian media published CCTV photos of an armed Roslyakov walking through the school in a white t-shirt, with a shotgun in his hands and wearing gloves.

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His mother, a nurse, was helping to treat victims at a local hospital after the shootings, unaware at the time that her son was accused of the rampage and was already dead.

Fifty-three people were wounded, including 12 in serious condition.

Russian President Vladimir Putin told reporters in Moscow that investigators were trying to work out the motive for the fatal attack.

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

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.

"He was walking around and shooting students and teachers in cold blood," said Sergei Aksyonov, the regional leader in Crimea.

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

An explosive device packed with metal objects went off in the cafeteria of the college. ( Kerch FM News via AP )

A second explosive device was found among the suspect's personal possessions and was disarmed.

Some Russian news reports said the shooter had left his backpack containing the explosive device in the cafeteria and remotely detonated it before he started shooting.

"I heard an explosion and saw glass shards and window frames falling down," student Roman Voitenko said in remarks broadcast on Russian state television.

Another student, Semyon Gavrilov, said he had fallen asleep during a lecture and was awakened by the sound of shooting. He looked around and saw a young man shooting at people, he said.

"I locked the door, hoping he wouldn't hear me," Gavrilov told the Komsomolskaya Pravda newspaper.

He said police arrived about 10 minutes later to evacuate people and he saw dead bodies on the floor and charred walls.

A victim of the Crimea attack is taken away in an ambulance. ( Viktor Korotaev/Kommersant Photo via AP )

Soon after the attack, Russian officials said they were investigating the possibility that it was terrorism.

However, the Investigative Committee, the state body that investigates major crimes, said later that it was not terrorism, but mass murder.

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

'Bodies of children everywhere'

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

The college is for students who have left high school and are studying for a technical trade. Students as young as 14 attend.

The Investigative Committee said initial information was that an explosive device packed with metal objects had gone off in the cafeteria of the college.

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

Russian officials said military planes were ready to evacuate casualties for treatment. ( Kerch FM News via AP )

Anastasia Yenshina, a 15-year-old student at the college, said she was in a toilet on the ground floor of the building with some friends when she heard the sound of an explosion.

"I came out and there was dust and smoke, I couldn't understand, I'd been deafened," she said.

"Everyone started running. I did not know what to do. Then they told us to leave the building through the gymnasium."

Russian Defence Minister Sergei Shoigu said four military planes were ready to evacuate casualties for medical treatment, the Interfax news agency reported.

It was the greatest loss of life in school violence in Russia since the Beslan terrorist attack by Chechen separatists in 2004, in which 333 people were killed during a three-day siege, many of them children, and hundreds were wounded.

Mr Shoigu was also cited as saying that space in military hospitals in Crimea was available for the victims.

Photographs from the scene of the blast posted by local media outlet Kerch.FM showed that the ground floor windows of the two-storey building had been blown out, and that debris was lying on the floor outside.

Reuters and AP