Russia’s submarine patrols have reached a level of operation not seen since the Cold War, according to its navy chief.

Admiral Vladimir Korolev told state media that Russian submarine crews had spent more than 3,000 days on patrol last year.

The patrols match the activity of the country before the Soviet collapse in 1991, which Mr Korolev told state media is an “excellent level”.

He made the remarks at the launch of the Yasen-class Kazan, a new nuclear-powered attack submarine, Sky News reported.

Russia’s navy, along with its military, suffered after 1991 when a lack of money caused many ships to be kept in harbour and others scrapped, but it has revived its strength in recent years through an arms modernisation programme, the Associated Press reports.

Mr Korolev said the new submarines are quieter and therefore more difficult to track than other machines. “It represents the cutting edge of nuclear submarine design,” he said on TV.

The submarines are fitted with torpedoes and Kalibr cruise missiles, and another five similar machines are expected to be built by 2023, The Times reported.