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

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.

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.

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.

A Royal Navy submarine was authorized to surface close to a Russian ship "strictly as a deterrent measure," British Defense Secretary John Healey said.