A Russian ship in the North Sea is being monitored by the British and Dutch navies after it was spotted earlier this week, broadcaster NOS said on Thursday.

The vessel, the Yantar, is used for gathering intelligence and mapping underwater infrastructure, Britain’s defence minister John Healey told MPs, describing the incident as “another example of growing Russian aggression.”

“I changed the navy’s rules of engagement so that our warships can get closer and better track the Yantar. So far, the ship has complied with international rules of navigation,” he said.

The defence secretary said it was the second time the vessel had entered British waters in recent months.

An NH90 helicopter from the Netherlands and the Dutch coastguard were also involved in the monitoring operation.

The Dutch defence ministry told broadcaster NOS the ship was in the “exclusive economic zone” of the North Sea, which is part of international waters, and where the Netherlands has jurisdiction.

The ship can operate drones capable of reaching the ocean floor, British media said. Undersea infrastructure is crucial for energy supply through power cables and pipelines, while more than 95% of internet traffic is also secured via undersea cables.