The UK on Friday blacklisted another 100 tankers from the shadow fleet.
Prime Minister Keir Starmer announced the sanctions at a meeting of leaders from the Joint Expeditionary Force (JEF) security alliance in Norway.
The aim is to increase the pressure on Russia to seek a peace deal in Ukraine.
The targeted tankers have carried cargo worth more than $24bn since the beginning of 2024.
Some vessels have also been involved in damaging critical infrastructure such as subsea cables, the UK added.
This would be the country’s biggest single package of ship sanctions, Starmer’s office said.
The UK has already designated 133 tankers, including 40 in the most recent round of sanctions in February.
Most of the ships have not been previously targeted before by the US and EU. The total number of ships targeted by the three sanctions regimes now tops 400, according to a TradeWinds tally.
The British-led JEF group of 10 northern European nations, including Denmark, the Netherlands, Finland and Sweden, complements the Nato military alliance.
Starmer said: “Every step we take to increase pressure on Russia and achieve a just and sustainable peace in Ukraine is another step towards security and prosperity in the UK.
“We will do everything in our power to destroy [President Vladimir Putin’s] shadow fleet operation, starve his war machine of oil revenues and protect the subsea infrastructure that we rely on for our everyday lives," he added.
In March, the British government removed Turkey’s Active Shipping & Management from its Russian sanctions list after more than a year.
Istanbul-based Active, controlled by Turkish industrialist Mehmet Ali Umur, was designated by the British government in February 2024 for allegedly providing benefits or support to Russia.
It was managing 17 vessels, including 13 tankers, at the time of the listing, which included some calling at Russian ports following the invasion of Ukraine.
The UK Treasury said the company was removed from the list and was no longer subject to an asset freeze.
The ministry did not say why the measure was being lifted.
