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".

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".

The nuclear-powered hunter-killer submarine surfaced close to the Yantar to let the Russian ship know it was being watched.

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

The British defense secretary told Parliament that the Yantar, which he described as a Russian spy ship, had come near Britain’s coast for the second time in a few months.

In a message to Vladimir Putin, Defence Secretary John Healey said ‘we see you, we know what you are doing and we will not shy away from robust action to protect this country’

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.

A Russian spy ship entered British waters twice in recent weeks, prompting the UK to deploy Royal Navy ships, Royal Air Force planes and a submarine, Defence Secretary John 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.