Russia has boosted the number of ships flying its own flag by more than one third as it looks to keep oil flowing by avoiding tanker seizures from other countries.

Between January 2025 and June 2026, some 107 vessels were added to Russia’s flag registry, marking a 36 per cent increase from 280 to 382 vessels, according to analysis by the Centre for Research on Energy and Clean Air (CREA) published on Friday.

European nations and the US have ramped up seizures and detentions of tankers violating maritime law by flying false flags and working as part of Moscow’s so-called ‘shadow fleet’, which carries Russian oil in defiance of Western sanctions.

Several European states have confirmed they are considering stricter maritime intervention protocols to target vessels believed to be circumventing trade sanction, in a move that was blasted by Russian president Vladimir Putin as “nothing less than piracy and robbery”.

Vessels sailing under the false flags are technically uninsured and stateless by law, and as Western countries scale up operations against them, they have joined the Russian ship registry with limited other options.

At least 23 shadow fleet ships sailing under false flags have been detained since December 2024, according to maritime analysts Windward AI. It adds that the UK and EU have sanctioned more than 650 ships since the end of 2023, all of which were deployed to ship sanctioned oil from Russia, Iran or Venezuela.

In June, Russian tanker Smyrtos was detained by British authorities in international waters in the English channel, with the shipmaster, an Indian national, charged by prosecutors with “directly or indirectly supplying or delivering by ship prohibited oil or oil products from Russia to a third country”.

Since the crackdown began, the number of shadow vessels flying false flags has dropped to 45 by the end of June, from a peak of 101 in October 2025, the CREA said. Some 87 per cent of the vessels added to the Russian registry were already sanctioned at the time.

But by hoisting the Russian flag, these ships become effectively immune to European seizure and “renders obsolete the sanctions mechanism European navies have used to interdict them”, the CREA says.

“‘Shadow’ fleet vessels have been funnelled into the Russian ship registry as their other options have been slowly closed off,” the CREA said in its report.

“Russian ‘shadow’ vessels had relied on open registries, due to their low registration costs, light regulation and opaque ownership. Under diplomatic pressure from sanctioning countries, many open registries began significantly withdrawing their flagging services for ‘shadow’ vessels.”

But countries running the open registries, including Panama and Comoros, have imposed stricter monitoring under pressure from the West, and some have partially or entirely removed sanctioned ‘shadow’ vessels from their registry, leaving them stateless and open to being detained for violating maritime law.

“Following pressure from sanctioning jurisdictions, Barbados and Palau removed all sanctioned ‘shadow’ vessels from their registries, while Panama cut the number of sanctioned ‘shadow’ vessels in their registries by almost two-thirds since May 2025,” the report read.

Cameroon’s move to cut more than 30 ships from its registry is the reason the UK was able to board and seize the sanctioned tanker Smyrtos in June.