The UK is exploring military options if a Russian spy ship sails closer to British shores after its crew used a laser to target RAF pilots monitoring its progress.
Defence Secretary John Healey said the UK was ready to respond if the ship heads south from its current position north of Scotland.
The frigate HMS Somerset and RAF P-8 Poseidon aircraft have been keeping watch on the Yantar, which is designed for gathering intelligence and mapping crucial undersea cables, after it entered wider UK waters this month.
Mr Healey said the frigate and planes had been deployed to “track this vessel’s every move, during which the Yantar directed lasers at our pilots”.
“That Russian action is deeply dangerous.”
Foreign Secretary Yvette Cooper, in Berlin for a meeting with her German counterpart, said the UK would be “vigilant and determined” in its response to Vladimir Putin’s Russia.
Russia denied that it was “interested in British underwater communications” and accused the UK of being “Russophobic” and “whipping up militaristic hysteria”.
The voyage of the Yantar is seen as further sign of Russian interference in Europe, following aircraft and drones crossing into Nato airspace and a sabotage attack on a Polish rail line used to supply Ukraine.
At a Downing Street press conference, Mr Healey said: “My message to Russia and to Putin is this: We see you. We know what you’re doing. If the Yantar travels south this week, we are ready.”
He warned the UK was facing a “new era of threat” to its security.
In January, it emerged that the Yantar was caught lurking over undersea cables and was warned off by a Royal Navy nuclear-powered attack submarine which surfaced nearby, having secretly followed the vessel.
The UK and Nato allies are increasingly concerned about the risk Moscow poses to offshore cables, pipelines and other infrastructure critical to internet connectivity.
Attacks on undersea cables could cause “catastrophic disruption” to the financial and communications systems Britons rely on, the National Security Strategy Committee warned in a September report.
The Yantar has been within the UK’s exclusive economic zone, which extends up to 200 nautical miles – about 230 miles – offshore, but has been on the edge of Britain’s territorial waters, within 12 nautical miles (13.8 miles) from the coast.
The incident with the laser is understood to have happened within the last fortnight.
Mr Healey said: “Clearly, anything that impedes, disrupts or puts at risk pilots in charge of British military planes is deeply dangerous.
“This is the first time we’ve had this action from Yantar directed against the British RAF.
“We take it extremely seriously. I’ve changed the navy’s rules of engagement so that we can follow more closely, monitor more closely, the activities of the Yantar when it’s in our wider waters.
“We have military options ready should the Yantar change course. I’m not going to reveal those, because that only makes President Putin wiser.”
A repeat of the submarine response could be one military option on the table, or warships could follow the example of the Dutch navy, which escorted the Yantar out of the Netherlands’ part of the North Sea earlier this month.
In Berlin, Ms Cooper suggested Russia’s actions were motivated by frustration at the lack of progress in Ukraine.
She said: “Russia has failed in its military objectives over the course of this year, so as a result, what we have seen them try to do is to seek continually to escalate.
“We can see the approach they are taking, we have no illusions about what they are doing. We see what Putin is doing and we understand and we will continue to be vigilant and determined in our response.
“Just as we have been about incursions into Nato airspace, just as we are being now in terms of identifying the Russian spy ship in UK waters and just as we have continued to be in response to sabotage threats that we have seen across many different European countries as well.
“It will not deter us from supporting Ukraine, quite the opposite, because we know Ukraine’s security is our security.”
In a message posted on its Telegram channel, Russia’s embassy in London said: “The endless accusations and suspicions of the British leadership cause only a smile. Our country’s actions do not affect the interests of the United Kingdom and are not aimed at undermining its security. We are not interested in British underwater communications.
“However, London, with its Russophobic course and whipping up militaristic hysteria, contributes to the further degradation of European security, creating the prerequisites for new dangerous situations.
“We call on the British side to refrain from destructive steps that exacerbate the crisis on the European continent.”
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