A spate of unexplained explosions affecting oil tankers with recent links to Russian ports has raised concerns within the international maritime sector, prompting speculation that the incidents may form part of a covert sabotage campaign.
According to a recent investigation by the Financial Times, five such attacks have occurred since the beginning of 2025, with no group claiming responsibility and no state officially implicated.
The most recent incident occurred last week off the coast of Libya. The Greek-owned tanker Vilamoura, operated by the Cardiff Group and controlled by Greek shipping magnate George Economou, suffered significant damage after its engine room was flooded. The cause, as in earlier cases, has not been officially confirmed, but experts point to a deliberate act targeting the vessel’s hull.
The attacks have predominantly taken place in the Mediterranean, with one confirmed case in the Baltic Sea. They follow a discernible pattern: all five tankers had docked at Russian ports weeks before being targeted. This detail has led some observers to propose a connection with Ukraine, whose security and intelligence services have carried out multiple clandestine operations against Russian infrastructure and logistics since the full-scale invasion in 2022. However, Kyiv has not commented on the matter.
A security adviser quoted in the Financial Times stated that Ukraine was “initially suspected” of involvement. However, the Vilamoura attack, which appears to have originated from the vessel’s keel rather than its side, suggests the possibility of alternative actors or techniques not previously associated with Ukrainian operations.
Further complicating the picture is the geographical context. Four of the damaged vessels made port calls in Libya shortly before the incidents. Libya remains fractured between rival factions, some of which finance themselves through oil exports. This has led to theories that local groups—or those with external backing—could be attempting to disrupt competitors or signal broader geopolitical intentions.
All affected vessels were Greek- or Cypriot-owned. In addition to Vilamoura, the Seacharm and Seajewel, both damaged earlier in the year, are operated by Thenamaris, a prominent Greek shipping firm owned by Nikolas Martinos. The Grace Ferrum, attacked near Libya in February, is operated by the Cypriot firm Cymare.
The fifth vessel, Koala, suffered an explosion in February while docked in the Russian port of Ust-Luga. Unlike the other four, this tanker was later sanctioned by the European Union in May 2025 for breaching the G7-imposed $60 per barrel price cap on Russian oil. However, tracking data indicates that none of the other tankers involved appear to have violated the oil price restrictions. Most had visited Russian ports that handle Kazakh-origin crude, which is not subject to sanctions.
Martin Kelly, head of intelligence at maritime security firm EOS Risk Group, stated that while there are similarities among some of the incidents, not all follow the same operational pattern. “There are alternative scenarios to consider, including the possibility of Libyan actors or states with both the technical capability and strategic motive to carry out such attacks,” Kelly said.
The operational methods remain under scrutiny. In previous attacks, damage appeared externally inflicted, suggesting limpet mines or similar devices. The recent Vilamoura incident, with damage to the vessel’s underside, has prompted speculation about divers or submersibles capable of planting explosive devices below the waterline—methods that require considerable expertise and access to restricted areas.
The series of explosions has drawn attention to the so-called “shadow fleet”—a term used to describe vessels that operate in legally grey areas, often servicing Russia’s energy export needs while seeking to avoid regulatory oversight. The Koala’s inclusion in the EU’s sanctions list appears to confirm the existence of loopholes in current enforcement mechanisms, particularly regarding the monitoring of origin and pricing of oil cargoes.
