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.

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.

Britain on Wednesday warned that it faced a growing threat of aggression from Russia, asserting that a Russian spy ship had passed by the English coast for the second time in three 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.

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.