Published by Global Banking & Finance Review®
Posted on July 9, 2025
4 min readLast updated: January 23, 2026
Greek tankers are boosting inspections near Russian ports after mysterious blasts damaged vessels. Measures include underwater checks amid security concerns.
By Jonathan Saul and Renee Maltezou
LONDON/ATHENS (Reuters) -Greek shipping companies calling at Russian ports are boosting their vessels' defences after a series of mysterious blasts in recent months have damaged tankers linked to Moscow's oil trade according to six Greek shipping and security sources.
The measures include underwater inspections by divers to check for foreign objects, two of the Greek sources familiar with the strategy said.
Western countries have hit Russia with waves of sanctions over its war in Ukraine and the Group of Seven major powers has separately imposed a price cap of $60 a barrel on Moscow's oil exports, which are the country's economic lifeline.
Much of Russia’s oil is now exported by a so-called "shadow fleet" of unregulated tankers, but shipping data shows Greek-owned ships, part of the world's largest tanker fleet, have also been carrying Russian crude.
Greek shipping companies say transporting Russian oil sold within the G7 price cap remains a legitimate trade. However, this year's explosions on at least six vessels that have called at Russia's Baltic Sea port of Ust-Luga and its Black Sea port of Novorossiysk have unsettled the market, people familiar with the matter said.
Vessels waiting outside Russian anchorages and other zones would shift their positions at varying times to make their location less predictable, while crews were on alert for any movement around their ships, one of the Greek sources, who declined to be identified due to the sensitivity of the matter, said.
Two of the other sources added that other measures such as remote underwater checks of the hulls were also being explored.
So far, no official results of various probes into the incidents have been released, though security sources have said limpet mines, which get attached to a target by magnets, were likely behind some of the blasts.
Three security sources advising the industry, but not directly involved in the investigations, said they were working on the possibility that Ukrainian teams were involved in some of the blasts, given Kyiv's objections to Greek ships' involvement in the transport of Russian oil.
Ukraine has refrained from commenting on those incidents in the past and Ukraine's military intelligence agency and its security service both declined comment when contacted about this story.
In the latest incident on July 6, the Eco Wizard LPG (liquefied petroleum gas) tanker experienced a series of blasts at Russia's Ust-Luga port.
Moscow's transport ministry said the tanker experienced a minor leak of liquid ammonia while it was loading and an inspection of the vessel by divers was planned.
Its Greek-based operator Stealth Gas declined to comment, while other sources said the blast suggested an explosive device caused the damage.
Earlier last week, a blast damaged Greek oil tanker Vilamoura as it was sailing off the Libyan coast, which its operator TMS Tankers said was likely caused by an external explosive device, citing an initial investigation.
Asked about an investigation launched earlier this year after tanker Seacharm was damaged in a blasts in February, the Greek authorities declined comment saying the information was classified. Italian authorities, which at the time opened a terrorism investigation into damage to another tanker, the Seajewel, have since offered no further updates on the probe.
MEDITERRANEAN CONNECTION
Four of the tankers that suffered blasts this year, had Greek operators with a further one based in Cyprus, according to data analysis of the companies.
Four of the six ships were sailing towards the Mediterranean coast after calling at Russian ports, marking the first time in decades when such incidents involved non-military vessels in the central Mediterranean.
Vessels with Russian port calls faced "increasing exposure to sabotage by organised state-sponsored actors or proxy groups amid the Russia-Ukraine conflict", Corey Ranslem, CEO of British maritime cyber defence and risk intelligence company Dryad Global, told Reuters.
"Despite the Mediterranean’s relative stability compared to high-risk regions like the Red Sea, vulnerabilities persist during transit or at less secure anchorages, such as off Libya, where oversight is limited," Ranslem said.
Ellie Shafik, head of intelligence with UK based maritime risk management company Vanguard Tech, said patterns of activity and the likelihood of involvement suggested "Ukrainian state or state-aligned actors" were likely to have been involved in some of the incidents.
"The strategy of perpetrators appears to be deliberate covert maritime sabotage of vessels using limpet mines," she said.
"This method ensures engine-room flooding and immobilization without causing the total destruction of the vessel or crew casualties. The nature of the sabotage is indicative of professional, military-grade capabilities."
(Reporting by Jonathan Saul and Renee Maltezou, additional reporting by Yannis Souliotis, Tom Balmforth, Emilio Parodi and Gleb Stolyarov; editing by Rachel Armstrong and Tomasz Janowski)
Greek shipping companies are enhancing vessel defenses, including underwater inspections by divers and remote checks of hulls to detect foreign objects.
This year, at least six vessels that called at Russian ports have experienced explosions, raising alarms about potential sabotage linked to the ongoing Russia-Ukraine conflict.
Security sources suggest that limpet mines, which attach to targets using magnets, are likely behind some of the blasts affecting the tankers.
Western sanctions on Russia over its war in Ukraine have led to the emergence of a 'shadow fleet' of unregulated tankers, complicating the landscape of oil exports.
The G7 has imposed a price cap of $60 a barrel on Russian oil exports, which Greek shipping companies argue allows for legitimate trade as long as the oil is sold within this limit.
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