Military operation conducted to deter Russian submarines suspected of

British and Norwegian militaries led a weekslong operation to deter Russian submarines suspected of “malign activity” in the North Atlantic, the U.K. military said Thursday.

Defense Secretary John Healey said a frigate, planes and hundreds of personnel monitored a Russian attack sub and two spy submarines near undersea infrastructure north of the U.K. He said the Russian vessels eventually left after the operation that lasted more than a month.

Healey said his message to Russia was “we see your activity over our cables and our pipelines and you should know that any attempt to damage them will not be tolerated and will have serious consequences.”

Representatives of Norway’s defense and foreign ministries, as well as its armed forces, did not immediately respond to requests for comment.

British officials have tried to keep Russia in the international spotlight even as the world’s attention is focused on conflict in the Middle East. They have also stressed the overlap between conflicts there and in Ukraine, saying Russia has supplied Iran with drone parts and other support.

Healey told a news conference that “Putin would want us to be distracted by the Middle East,” but Russia is the main threat to the U.K. and its allies.

“We will not take our eyes off Putin,” he said.

The U.K. government announced late last year that it and Norway had formed an alliance to “hunt Russian submarines” and protect communication lines in the North Atlantic as part of a defense agreement between the two countries.

Central to the deal is a new joint fleet of anti-submarine warships — in response to a 30% increase in the presence of Russian ships in U.K. waters over the last two years, the U.K. said in December. The fleet includes eight British vessels and at least five Norwegian vessels.

Healey had said the pact would enable the two countries to “patrol the North Atlantic as one, train together in the Arctic, and develop the advanced equipment that will keep our citizens safe now and into the future.”

In late March, the U.K. said its military was ready to seize ships suspected of being part of Russia’s “shadow fleet” of vessels shipping oil in violation of international sanctions over Moscow’s war on Ukraine. Previously, Britain had only helped France and the U.S. monitor ships before they were boarded.

“We are ready to take action” against the vessels, Healey said.