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.

Britain’s defence minister has warned Russian President Vladimir Putin that “we will not shy away from robust action” after telling Parliament that a Russian spy vessel had been operating in UK waters this week.

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.