Nations on the Baltic Sea, along with NATO, have stepped up security after a third incident of suspected sabotage to underwater infrastructure in a month.

Finnish police say authorities detained a ship linked to neighboring Russia as they investigate whether it damaged a Baltic Sea power cable and several data cables.

Finland's public transport agency said on Wednesday that an oil tanker suspected of damaging undersea cables in the Baltic Sea has been found to have serious deficiencies and will not be allowed to operate until repairs have been made.

Finnish police have reported finding the anchor responsible for severing an undersea internet cable connecting Finland to Estonia. Last month, Finland detained the Eagle S, an oil tanker transporting Russian oil,

Finnish police said on Tuesday they have recovered a lost anchor from the bottom of the ocean as part of an investigation of suspected sabotage against power and internet cables in the Baltic Sea. Finland last month seized the Eagle S tanker carrying Russian oil on suspicion that the vessel had damaged the Finnish-Estonian Estlink 2 power line and four telecoms cables by dragging its anchor across the seabed.

The anchor of the Eagle S oil tanker has been recovered from the bed of the Baltic Sea during an inquiry into the ship's possible involvement in sabotage of maritime energy and communication cables. The EU says the tanker belongs to the so-called Russian shadow fleet.