Military police secured the historic Serafimovskoye Cemetery in St. Petersburg on Saturday for the funeral of 14 navy servicemen who had died in a submarine fire.

The event was closed to the press. However, several senior military and civilian officials were seen paying their respects.

Details of Monday's blaze in the Barents Sea are still scare with Putin’s Defence Ministry claiming the sailors were killed by toxic fumes from the fire.

Some men survived the fire but the military hasn't said how many while authorities denied reports the incident was caused by a gas explosion. Officials didn't name the nuclear-powered vessel, but Russian media reported that it was the Kremlin's most secret submersible, the Losharik.

The vessel was based in Severomorsk in northern Russia. Despite the official secrecy, Russian media have widely reported that the craft was a S-12 or AS-31, nicknamed "Losharik", which had been exploring the Arctic seabed in the Barents Sea.

The crew have been linked in media reports to a top-secret Russian military branch known as the Chief Directorate for Deep Water Research, or GUGI.

A military analyst for Russian newspaper Novaya Gazeta speculated the vessel might have been involved in testing new secret equipment or examining devices left on the sea floor by the United States.

Russia is known to be staking a territorial claim to the Arctic, on the basis that its continental shelf extends north under the ocean.

But competing claims by other nations - Canada, the US, Norway and Denmark - are being examined by the United Nations.

Vira Maritime