(Reuters) -Russia's military said on Friday that a blast that injured seven servicemen at a military academy in St. Petersburg was caused by the accidental detonation of World War Two-era ammunition, Interfax news agency reported.

Interfax news agency, quoting the Leningrad military district, said the servicemen were injured at the Budyonny Military Academy of the Signal Corps during a check of underground areas in St Petersburg, Russia's second largest city.

St Petersburg Governor Alexander Beglov said the blast was not linked to terrorism.

(Writing by Felix Light, Editing by Franklin Paul, Ron Popeski and Chizu Nomiyama)