The British navy said Wednesday that is ramping up measures to protect its waters from secret Russian operations after identifying a Russian spy vessel in UK waters for the second time in weeks.

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.

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.

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.

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

The Royal Navy of the United Kingdom has been closely tracking a Russian spy ship recently spotted in British waters, sparking concerns about Russia’s activities near the U.K.’s critical underwater infrastructure.