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.
He said the incident was “another example of growing Russian aggression”.
Healey added: “I also wanted President Putin to hear this message: we see you, we know what you’re doing and we will not shy away from robust action to protect this country.”
Russia describes Yantar as an oceanic research vessel and it is operated by the country’s Ministry of Defence.
Western nations have often tracked the ship operating in European waters and they suspect part of its mission has been to map undersea cables.
They also believe Russia has been stepping up this activity since it launched its full scale invasion of Ukraine.
As well as surveillance equipment the ship can operate submersible drones capable of reaching the ocean floor.
Undersea infrastructure is crucial for energy supply through power cables and pipelines, while more than 95% of internet traffic is also secured via undersea cables.
Healey said Yantar was currently in the North Sea, after passing through UK waters and being detected 45 miles off the British coast in the English Channel on Monday.
“For the last two days the Royal Navy has deployed HMS Somerset and HMS Tyne to monitor the vessel every minute through our waters,” he said.
“I changed the Royal Navy’s rules of engagement so that our warships can get closer and better track the Yantar. So far, the ship has complied with international rules of navigation.”
The defence secretary said it was the second time the vessel had entered British waters in recent months, with Yantar also detected “loitering over UK critical undersea infrastructure” in November.
He said an Royal Navy submarine had been authorised to surface close to Yantar “strictly as a deterrent measure” and “to make clear that we have been covertly monitoring its every move”.
“The ship then left UK waters without further loitering and sailed down to the Mediterranean,” he added.