Russia staged a nationwide test of its air-raid sirens today as Vladimir Putin’s state TV warned it could destroy the entire British army within two months.

The late-morning alert sounded across the country’s 11 time zones, with officials urging citizens not to panic but to switch on televisions or radios for emergency instructions.

Russia’s emergencies ministry said the system is designed to quickly warn the public in the event of war, disasters or other emergencies.

It told people: “On hearing a siren, you must remain calm and not panic.

“Turn on the television – any public channel or radio – and listen to the informational announcement.”