A Ukrainian Sea Baby unmanned surface vessel exploded near Berth 78 in Romania’s Constanța Port on June 5, triggering fresh tensions over the management of security incidents spilling over from the war in Ukraine and exposing apparent shortcomings in communications between Kyiv and Bucharest.

According to a Romanian government statement, the incident occurred at 10:28 local time. Authorities later said Ukraine had informed Romania that it had lost control of four explosive-laden naval drones, but only after port personnel had discovered one of the devices, around 6:00 in the morning, and Romanian officials contacted their Ukrainian counterparts.

The explosion, captured by public broadcaster TVR and other media outlets, highlighted the offensive capabilities of the specific Sea Baby drone (the class can be customised for specific missions), which can carry warheads weighing up to two tonnes and has been extensively used by Ukraine against Russian naval targets. Two such drones struck the Crimean Bridge in July 2023.

The Romanian government’s statement suggested that no prior warning had been issued by Kyiv. “The Romanian authorities requested the Ukrainian authorities to immediately notify the Romanian side in similar situations that may generate risks for Romania,” the statement said.

In a Facebook post published at 14:30, several hours after the explosion, the Ukrainian Navy said one of its unmanned boats had lost control after being affected by Russian electronic warfare and had drifted towards the Romanian coast.

“The Ukrainian Navy provided the necessary information to the Romanian Navy in order to prevent civilian casualties,” the statement read, without specifying when the information had been transmitted.

President Nicușor Dan said at a press conference in Constanta on June 6 that a report on the incident would be published within seven to ten days following consultations with the institutions involved.

He stressed that Russia, as the aggressor in the war, bears ultimate responsibility for such incidents and said Romania was adapting to evolving threats through the acquisition of new military equipment. “The Romanian institutions responded well to the challenge,” he said.

The episode came only one week after a Russian drone struck an apartment block in Galați, injuring two people. No official report has yet been released regarding that incident.

Questions over chronology and response

The sequence of events released by Romanian authorities raises several unanswered questions.

According to the government, Ukraine confirmed around 06:20 that four drones had gone missing (although the Ukrainian Navy mentions only one). However, a Ro-Alert warning advising residents of Constanța to avoid coastal areas and seek shelter was issued only around 11:20, almost one hour after the explosion in the port.

At 10:45, a commercial vessel located approximately 145km from Constanța reported observing two explosions, which authorities implied involved two additional drones (of the four reported lost by Ukraine). Tourists evacuated from beaches along Romania’s Black Sea coast were allowed to return around 15:00, despite one drone still being unaccounted for.

The government later stated that the fourth drone exploded in international waters, although no details were provided.

Romania’s Defence Ministry issued a brief statement after the incident stressing that the drone did not belong to the Romanian military and that maritime traffic monitoring falls under the jurisdiction of the Romanian Naval Authority.

By that time, however, images circulating in the media had already identified the device as a Ukrainian Sea Baby drone.

Sea Baby capabilities raise surveillance concerns

Developed in 2022 by Ukraine’s Security Service, Sea Baby unmanned surface vessels are approximately six metres long and two metres wide. Since 2025, newer versions have reportedly been capable of carrying payloads of up to 2,000kg over distances of 1,500km, using redundant communications systems and remote control centres.

The fact that such relatively large craft approached the Romanian coastline without being intercepted or detected earlier is likely to become one of the key issues examined by the forthcoming investigation.

Unlike aerial drones, maritime drones remain a relatively new challenge for coastal surveillance systems. However, Sea Baby platforms have been operational for almost four years and have featured prominently in Black Sea operations, suggesting that the threat itself cannot be considered unexpected.

Shadow fleet allegations emerge

The incident has also drawn attention to shipping linked to Russian oil exports.

Spotmedia reported, citing sources, that the Ukrainian drones had been pursuing the tanker Safeen Elona, which had departed from the Rompetrol terminal in Midia Năvodari and appears on Ukraine’s sanctions list targeting Russia’s so-called shadow fleet.

President Dan dismissed such reports on June 6 as “speculations”, noting that the vessel is not included in European Union or US sanctions lists.

While Safeen Elona does not appear on EU or US sanctions registers, it is listed by Ukraine. Maritime data indicate that the vessel left Midia Năvodari, about 20km north of Constanța, at 09:18 on June 5.

According to Spotmedia, at least 11 tankers designated by Ukraine as enemy targets have operated in Romanian territorial waters and docked in Romanian ports. Six of those vessels are also subject to European Union sanctions, while one has been sanctioned by the United States.

Defence Minister Radu Miruta explained that none of the six ships mentioned by Spotmedia, indeed on the sanctions list currently, entered a Romanian port after they were designated as part of the “ghost fleet” by the EU or the US. Again, this does not mean that they were not on Ukraine’s black list.

Broader implications

Beyond the immediate questions surrounding the chronology of the June 5 incident, the episode highlights the growing complexity of security challenges facing Romania as the war increasingly affects the wider Black Sea region.

The combination of Russian strikes close to Romanian territory, Ukrainian counter-operations against maritime targets and the presence of vessels associated with Russian oil exports is creating situations for which existing procedures appear only partially adapted.

The report promised by Dan is expected to clarify whether the shortcomings revealed on June 5 stemmed primarily from delayed information-sharing by Ukraine, deficiencies in Romania’s own warning mechanisms, or a combination of both.

Its conclusions could have implications not only for Romania’s defence posture, but also for the rules governing military coordination among Ukraine’s neighbours as the conflict enters its fifth year.