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’.

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 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

The Royal Navy has been monitoring a Russian spy ship after it entered British waters, 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.