Nato intelligence officials warned in September that Russia was building up a secretive submarine unit tasked with sabotaging undersea infrastructure, while Dmitry Medvedev, a former Russian president, said such cables were fair game because of Western “complicity” in the sabotage of the Nord Stream gas pipeline.

On Monday, the transport and communications ministry in Helsinki issued new crisis guidelines to the country’s population, which include information on what to do in the event of disruptions to telecommunications infrastructure.

With Russia now surrounded by Nato states in the Baltic, its waters are seen as most vulnerable to attempts to disrupt key energy and communications lines.

Most dramatically, the Nord Stream pipeline, which brought Russian natural gas to Germany, was blown up half a year after Russia invaded Ukraine. While investigations into that incident continue, the saboteurs are believed to have been sent from Kyiv.

In October last year, a Chinese cargo vessel damaged a gas line between Finland and Estonia with its anchor. The Chinese authorities’ explanation that the incident was an accident has been viewed with suspicion in the West.