The United Kingdom has confirmed that one of its Royal Navy nuclear-powered submarines surfaced close to the Yantar, a notorious Russian spy ship late last year, to make it clear it was being observed.

John Healey warned Vladimir Putin ‘we see you, we know what you are doing and we will not shy away from robust action’.

Defence Secretary John Healey said Russia "remains the most pressing and immediate threat to Britain", and added that "any threat will be met with strength and resolve".

Royal Navy submarine used to warn off Russian spy ship loitering over cables - The nuclear-powered hunter-killer submarine surfaced close to the Yantar to let the Russian ship know it was being watched.

Moscow’s intelligence ship Yantar enters UK waters in ‘another example of growing Russian aggression’, according to the Defence Secretary

Britain said it monitored a Russian spy ship in the English Channel in recent days and would strengthen its response to secret operations by Russian ships and aircraft in an effort to protect undersea cables.

The Royal Navy has been monitoring a Russian spy ship after it was spotted around UK waters earlier this week, the defence secretary has told MPs. John Healey said the vessel, Yantar, was used for gathering intelligence and mapping the UK's critical underwater infrastructure.

British Defence Secretary John Healey told parliament Wednesday the Royal Navy was tracking a "Russian spy ship" that passed through UK waters, warning Russia's President Vladimir Putin: "We know what you're doing".

The UK authorized the British submarine to surface closely to the Russian vessel to warn it off, British defense secretary Healey said.

A British official sent a public warning to Russian President Vladimir Putin on Wednesday after the Royal Navy started tracking the Russian spy vessel Yantar in British waters this week.