Finnish authorities have boarded an oil tanker suspected of being behind a number of cable cuts in the Baltic Sea.

On December 25, the Estlink 2 submarine cable - which carries electricity between Finland and Estonia - was cut.

Around the same time, three Internet cables connecting the two nations were severed - two of which are owned by Finnish operator Elisa and another owned by China’s Citic.

A fourth fiber optic cable running between Finland and Germany from Finnish group Cinia is also thought to have been cut.

Finnish Transport and Communications Agency (Traficom) said: "Cable outages may cause delays in customers' communication services. Traficom is currently investigating the impacts with the operators.

"Cable repair work will begin during the end of the week. The repair schedule depends on weather conditions, among other things."

It added: "The incident has not had an impact on Finland's security of supply. Finland is well prepared for various disruptions in electricity transmission and telecommunications."

At the exact time the 658MW Estlink 2 cable was cut, the Eagle S Panamax oil tanker was tracked crossing it. Registered in the Cook Islands, the ship was sailing from St. Petersburg, Russia to Port Said, Egypt.

"The Helsinki Police Department and the Border Guard have conducted a tactical operation on the vessel," the Finnish police said.

"The authorities have taken investigative measures on the vessel, with access there provided by the Finnish Border Guard and the Defense Forces helicopters.

"At this stage, the case is being investigated as aggravated criminal mischief. In this respect, the National Bureau of Investigation (NBI) is responsible for leading the criminal investigation. Customs is making preliminary inquiries on-site in regard to an aggravated regulation violation and is looking into details concerning the cargo."

This incident comes just a month after a ship was suspected of deliberately dragging an anchor 111 miles along the sea bed and severing two subsea cables in the Baltic Sea. That ship was also boarded, and investigations are ongoing.

Earlier this month, a terrestrial Internet cable connecting Sweden and Finland was cut in two separate locations.

In a news conference, Finland’s prime minister, Petteri Orpo, said that the latest cut "underlies the danger of the shadow fleet in the Baltic Sea."

While there is currently no direct evidence of Russian involvement, he continued: "Our main task is to find effective means to stop the shadow fleet. The shadow fleet pumps money into Russia’s war fund so that Russia can continue to wage its war in Ukraine against the people of Ukraine, and it has to be stopped."