Photo by Daniel Olah
Sweden has seized and subsequently released an oil tanker linked to Russia’s shadow fleet after it was suspected of causing a 12-kilometre oil slick in the Baltic Sea east of Gotland, in what authorities described as a landmark case in the campaign to hold sanctioned vessels to account.
The incident began in the early hours of Thursday 2 April, when a Swedish Coast Guard surveillance aircraft detected a mineral oil slick stretching more than 12 kilometres in the Swedish exclusive economic zone. The Flora 1, an ageing product tanker outbound from Russia and claiming to be headed for the Brazilian port of Santos, was identified as the prime suspect. Coast guard officers told Politico they had received contradictory information about the vessel’s actual destination. The tanker was escorted to anchorage south of Ystad, on Sweden’s southern coast, where it was boarded by coast guard and police officers on Friday 3 April as part of a preliminary investigation into suspected environmental crimes.
A vessel with a troubled history
The Flora 1 is listed on the EU sanctions register and has also been sanctioned by the UK and others for its role in the Russian energy sector, according to The Maritime Executive. Built in 2005, it had changed its identity three times in 2025 alone, and since 2023 had claimed successive registrations in St. Kitts and Nevis, Gabon, Panama, Djibouti, Palau, Benin, and Sierra Leone — the last of which was later confirmed as false, according to data from the ship registry database Equasis. At the time of boarding, the vessel was displaying Sierra Leone as its flag state, which investigators noted contributed to “various uncertainties” around the ship.
Daniel Stenling, deputy head of operations at the Coast Guard, said the boarding was a direct product of Sweden’s stepped-up maritime surveillance: “We act when we detect emissions. This is the result of our enhanced maritime surveillance, which we are conducting as a result of the deteriorating security situation in the Baltic Sea region.” He added that it was “without doubt interesting in this context that the ship is surrounded by various uncertainties in addition to being suspected of an oil spill. Whether this entails further criminal suspicions will be revealed by the investigation.”
Stenling also underlined the historic nature of the case: “As far as we know, this is the first time we have been able to trace a discharge to a vessel subject to sanctions, and which may be suspected of environmental crimes.”
Charges filed, but enforcement limited
Swedish prosecutors confirmed that two crew members were charged on suspicion of violating the Act on Measures to Combat Pollution from Ships, though neither was detained or arrested. The Swedish Prosecution Authority acknowledged the constraints it faced: “The spill occurred within Sweden’s economic zone, which means that the investigative measures we can take are limited. We have conducted the interviews that were deemed necessary and we will not take any coercive measures due to this suspected crime.”
The Flora 1 was released on Saturday 5 April after Cameroon confirmed the vessel’s registration in its maritime registry, resolving the flag uncertainty, and prosecutors concluded they could not prove the environmental violations. Without a legal basis for continued detention, the Coast Guard had no choice but to let the vessel sail. By late Sunday it was off Denmark, heading out of the Baltic.
Stenling noted that the outcome did not diminish the significance of the action: “The suspicions do not lead to prosecution, but shipping should know that Swedish authorities are working together to maintain order at sea. We are acting to increase maritime safety and protect the environment. If there is a suspicious vessel, we intervene based on the prevailing conditions.”
Political pressure and broader pattern
Civil Defence Minister Carl-Oskar Bohlin said on X that “the Russian shadow fleet, consisting of older, poorly insured tankers that evade sanctions, poses a significant security and environmental threat,” and told Politico that “the government views the incident with grave concern, even though this time it is not a matter of a large-scale oil spill.”
The Flora 1 case is the third boarding of a suspected false-flagged vessel by Swedish authorities this year, according to Politico. Sweden is also detaining two other vessels linked to Russia under the Swedish Transport Agency, whose captains have been arrested for providing false information to police. Both ships’ flag registries are believed to be fraudulent, and Sweden is requiring proof of valid registration and insurance before permitting them to sail.
The Baltic is one of Europe’s most environmentally sensitive seas — shallow, semi-enclosed, and slow to flush pollutants. The Flora 1 spill was not expected to reach shore, but Bohlin warned that a larger release could have had devastating consequences for marine ecosystems and the Swedish coastline.