NATO Secretary-General Mark Rutte says the military alliance will step up patrols in the Baltic Sea area as Finnish investigators work to establish whether a ship linked to Russia sabotaged undersea cables there this week.

The Finnish authorities said the tanker might be part of Russia’s shadow fleet, which emerged as a way to circumvent Western-imposed price caps on Russian oil transported by sea. The caps were introduced several months after President Vladimir V. Putin of Russia ordered the full-scale invasion of Ukraine in February 2022.