A military police vehicle at St Petersburg's Mozhaisky Military Space Academy where an explosion went off (Photo: TASS via Getty Images)

Vietnamese Ambassador to Russia Ngo Duc Manh said 25 Vietnamese students are pursuing courses at the academy.

Earlier, the Russian Defence Ministry said that three people were hurt in the blast but their lives are not in danger. Police sealed off the area around the academy as cadets and staff were leaving the grounds.

The Mozhaisky Military Space Academy is one of Russia’s largest military training establishments. It trains officers to serve in air and space defence and other branches of the armed forces.