LONDON - Ukrainian sea drones on Wednesday hit and disabled a tanker involved in trading Russian oil as it sailed through Ukraine's exclusive economic zone in the Black Sea to the Russian port of Novorossiysk, a Ukrainian official said.

The attack is the third sea drone strike in two weeks on vessels part of Russia's so-called "shadow fleet" - unregulated ships which Kyiv says are helping Moscow export large quantities of oil and fund its war in Ukraine despite Western sanctions.

War insurance costs for ships sailing to the Black Sea have spiked, with insurers reviewing policies daily as the conflict in Ukraine spills into sea lanes.

The Dashan tanker was sailing at maximum speed with its transponders off when powerful explosions hit its stern, inflicting critical damage on the vessel, the official at the Security Service of Ukraine (SBU) said. He made no mention of possible casualties in the incident.

TANKER IS UNDER WESTERN SANCTIONS

The strike on the Dashan, which is under European Union and British sanctions and is sailing without a known flag registry, was also confirmed by three maritime security sources.

There was no immediate comment from Russia on the incident.

Naval drones could be seen speeding towards the hulking tanker followed by powerful explosions as they reached it, video footage provided by the official showed.

Reuters was able to verify it was the Dashan tanker in the video by comparing the deck, cranes and structures with file imagery. The location and date were confirmed by the SBU source's account and ship tracking data.

"The SBU continues to take active measures to reduce petrodollar revenues to the Russian budget," said the official.

"Over the past two weeks, this is the third tanker of the shadow fleet put out of action that had helped the Kremlin circumvent international sanctions."

Russian President Vladimir Putin, who ordered a full-scale invasion of Ukraine in February 2022, threatened last week to sever Ukraine's access to the Black Sea in response to the attacks on tankers, which he derided as piracy.

Ukraine has been attacking Russian oil refineries for months, using long-range aerial drones to strike far behind the front lines of Moscow's war against Ukraine.

The strikes on the tankers represent a different line of attack.

There have been at least seven blasts on other tankers that called at Russian ports since December 2024 at locations including in the Mediterranean.

Ukraine is suspected of carrying out those attacks using limpet mines, maritime security sources said, but Kyiv has not confirmed or denied any role.

Tom Balmforth and Jonathan Saul/ Additional reporting by Monica Naime/Reuters