Russian submarine forces allegedly tested a technology in the Arctic this spring that could disable undersea infrastructure without leaving visible traces. The activity took place near the Spitsbergen archipelago and was detected by the United States, Britain and Norway, two Western officials told Reuters.

According to their account, the operation was conducted by the Russian Defense Ministry’s Main Directorate of Deep-Sea Research. Russian forces allegedly used deep-sea vehicles to test a system capable of disrupting undersea cables while leaving no obvious evidence of interference.

British, Norwegian and US forces tracked the Russian submarines during the operation. The vessels later left the area.

Reuters’ sources said the cables themselves were not damaged. They claimed the drills were intended to simulate how the technology could be used in the event of a conflict with NATO. The officials declined to explain how the system works.

Britain and Norway later handed Russia the findings of their investigation, according to the report. The move was intended to demonstrate that the two countries were aware of the tests and the capabilities of the new technology.

Norwegian Defense Minister Tore Sandvik said the joint operation was meant to show Moscow that covert activity in the area would not go unnoticed. He also warned that any attempt to strike NATO critical infrastructure would be detected and would have consequences.

The area is particularly significant because two fiber-optic cables run between Spitsbergen and mainland Norway. The lines stretch for about 1,400 kilometers and lie at depths of up to 2,700 meters.

The cables carry large volumes of satellite data to the SvalSat ground station, described as the largest of its kind in the world. The facility is part of NASA’s Near Space Network.