The Kremlin has accused Britain of plotting "mass raids" on Moscow's ships in a bid to stop Russian oil exports around the world.
Russia's foreign intelligence service, the SVR, is said to have accused Britain of planning to attack the country's "shadow fleet" - a series of vessels smuggling sanctioned goods through the world's waters.
According to reports from the SVR, the attacks would seem like accidents and cause significant environmental damage - leaving Nato's "hands untied" and allowing the alliance to justify further actions against Russia.
"British intelligence services are planning to use Nato allies to launch a mass raid on the 'shadow fleet'; for this purpose, an ecological catastrophe in international waters is being prepared," it claimed.
"The impetus for such a campaign, according to London's plan, should be given by a resonant incident with one or several tankers," Kremlin bosses wrote.
"The plan provides for the organisation of a major sabotage, the damage from which will make it possible to declare the transportation of Russian oil a threat to all international shipping.
"This will untie the West's hands in choosing methods of counteraction."
REUTERS
|Moscow could be preparing to commit false flag attacks on its own fleet of ships to deter the West from hitting them with more sanctions
But the report has prompted fears that Russia is preparing for one of its old, barely-seaworthy vessels to break down of its own accord.
That could set off a major oil spill - with the Kremlin publishing the documents to preemptively shift the blame.
Dr Sidharth Kaushal, a research fellow at defence and security think tank Rusi, told The Telegraph: "One interpretation might be that the Russians are insuring themselves against something breaking down or sinking, in a way that creates a pretext for restricting [their movement across the ocean]."
Since the beginning of the year, at least six tankers have suffered from unexplained explosions.
So far, the blame has landed largely on Ukraine because all of the tankers were docked in Russian ports, with some carrying Russian oil.
Britain has banned the maritime transportation of Russian oil - as the country's energy exports are funding the war in Ukraine.
GETTY
|PICTURED: A suspected 'shadow fleet' tanker. Russian oil companies are using a complex network to obscure ownership and evade sanctions
Last year, 30 per cent of Russia's federal budget came from sales of oil and gas.
But investigators believe Western cash is still funding the Russian state, as oil companies manage to circumnavigate the sanctions through the use of the "shadow fleet".
The ships' flags are changed regularly, while onboard automatic identification systems are turned off.
The oil is often transferred from one ship to another before it reaches its destination.
A spokesman for the NCA said: "Today, the National Crime Agency has issued an alert to financial institutions and other members of the UK regulated sector in relation to the sale of Russian oil and gas through the use of Shadow Fleet vessels and front companies.
"Sanctions imposed on Russia as a result of its invasion of Ukraine have had a significant impact on its ability to see oil and gas it produces.
"However, in an effort to circumvent these controls, Russian oil trading companies are utilising a complex network of companies with deliberately obscure ownership structures to evade sanctions whilst accessing Western finance and professional services in order to continue to fund the Russian state."