Investigators believe the group used a yacht rented from the German port of Rostock under false identities to transport explosives to the site. Traces of the military-grade explosive octogen were later discovered on board.
According to German authorities, Serhii K. was “urgently suspected” of coordinating the attack alongside others. He faces charges of causing an explosion, committing anti-constitutional sabotage, and destroying infrastructure.
The arrest marks a breakthrough in a complex investigation that has stretched across several countries. Sweden and Denmark closed their probes without naming suspects earlier this year, while Germany pressed ahead with its case, focusing on a small team of divers and support staff thought to have carried out the mission. Reports from Western officials have pointed to possible links with Ukrainian networks, though Kyiv has consistently denied any involvement.
The suspect will be transferred to Germany to face a federal judge in Karlsruhe.