British forces have boarded and seized a Russian shadow-fleet oil tanker attempting to transit the English Channel, Prime Minister Keir Starmer announced Sunday.

The operation, confirmed by the UK Ministry of Defence, targeted the vessel Smyrtos. Starmer stated in a post on X that the successful operation "delivers yet another blow to Russia and reminds those fuelling [Russian President Vladimir] Putin’s war in Ukraine that we will not let them hide."

The Ministry of Defence confirmed the early Sunday seizure, with Defence Secretary Dan Jarvis adding in a statement, "Russia relies on its shadow fleet to fund its conflict in Ukraine and our interdiction delivers a blow to Putin’s illegal war." He also paid tribute to the "skill, professionalism and courage" of the armed forces involved.

The operation lasted six hours, according to the ministry. The vessel Smyrtos will be provisionally moved to an anchorage off the South Coast of England and monitored for any environmental or safety concerns.

This incident follows similar actions by French authorities last month, which, with UK support, intercepted an oil tanker suspected of being part of the shadow fleet. In January, French forces impounded another suspected Russian tanker, the Grinch, and in March, the Deyna was detained in Marseille.

Oil revenue is a critical component of Russia's economy and helps finance its ongoing war in Ukraine. Russia is understood to be utilizing a vast fleet of hundreds of ships to circumvent international sanctions imposed due to the conflict. The UK and its allies have committed to cracking down on this "shadow fleet."

According to the UK Ministry of Defence, Britain has so far imposed sanctions on over 500 vessels. These measures are reportedly having an impact, with Russia's oil and gas revenues declining by 24 percent in 2025 compared to the previous year.

Several Western nations have implemented sanctions against Russian vessels following Russia's full-scale invasion of Ukraine in 2022. Russian President Vladimir Putin has previously condemned the capture of Russian-linked vessels, characterizing such actions as "piracy."