Russia is using a network of more than 70 marine research vessels to spy on energy and defence infrastructure in the North Sea, TV current affairs show Pointer has claimed.

Researchers for the programme studied open-source location data and more than 1,000 messages in Morse code sent by Russian ships in the exclusive economic zone (EEZ) covered by EU nations and the UK.

The ships made more than 400 voyages into the area since the start of the full-scale invasion of Ukraine, ostensibly to carry out hydrographic research or rescue operations.

The investigation identified 54 journeys in which the vessels behaved suspiciously by sailing unusually slowly, moving in zig-zag patterns or stopping altogether.

The erratic movements were mostly observed in the vicinity of critical infrastructure such as wind parks, military installations and the Baltic connector gas pipeline between Estonia and Finland.

Researchers said some of the vessels were equipped with military radar, mini-submarines and underwater drones, and had armed guards on board: “The ships appear to have a double function so that they can be deployed for military purposes.”

“Sabotage”

James Appathurai, acting assistant secretary-general of Nato, said the aim of the missions was to compile information on critical infrastructure “with the aim of sabotaging it”.

“In the last six months we have seen the threat against our nations increase,” he told Pointer. “It includes sabotage, political interference, disinformation, cyber attacks, enforced migration and attacks on critical infrastructure.

“These are all part of a pattern that we need to defend ourselves against. We are doing a lot but we are still not adequately prepared.”