British forces intercepted a sanctioned oil tanker believed to be linked to Russia’s so-called “shadow fleet” during a six-hour operation in the English Channel.

The U.K. Ministry of Defence said the operation took place in international waters more than 12 nautical miles from the British coast. Royal Marines boarded the tanker Smertos with support from specialist officers from the National Crime Agency and assistance from the Royal Air Force.

British Prime Minister Keir Starmer described the operation as “another blow to Russia,” saying it demonstrated that those helping to finance Moscow’s war in Ukraine would not be allowed to operate with impunity.

Ukrainian Foreign Minister Andrii Sybiha welcomed the move, describing Russia’s shadow fleet as a tool supporting the country’s war effort and arguing that every vessel disrupted reduces funding available to Moscow.

The operation forms part of broader Western efforts to tighten enforcement of sanctions and curb attempts to circumvent restrictions on Russian oil exports.