British forces are preparing to board and detain vessels linked to Russia's so-called shadow fleet in British waters after the prime minister approved military action. The ships are accused of operating without valid national flags to evade sanctions on oil exports that help finance Russia’s war in Ukraine. Government ministers identified a legal basis earlier this year allowing the use of military force to intercept sanctioned vessels.

Specialist units, including the Royal Navy, Royal Marines and the Special Boat Service, have completed training for a range of scenarios, including the possibility of armed resistance. Officials are using ship-tracking technology to monitor sanctioned vessels and identify targets weeks before they reach British waters. The government has imposed sanctions on hundreds of ships believed to be involved in transporting most of Russia’s crude oil exports.

The prime minister said the action is intended to weaken President Vladimir Putin’s ability to profit from rising oil prices and fund the war effort. The move comes as Britain works with northern European allies to counter ongoing security threats from Russia, despite global attention being focused on conflict in the Middle East. Opposition figures have supported efforts to block sanctioned ships but questioned whether the armed forces have sufficient resources.