Germany’s maritime authorities (CCME) said on Friday that the Panamanian-flagged ship, known as Eventin, had lost power and steering, meaning tugboats were deployed to secure the vessel.

German foreign minister, Annalena Baerbock, blamed Moscow, saying in a statement that by “ruthlessly deploying a fleet of rusty tankers”, Russian President Vladimir Putin was “circumventing” sanctions and threatening European security.

Russia, which previously declined to respond to accusations that it uses a shadow fleet, has not yet commented on this incident.

The US, UK and the EU have imposed sanctions on Russia’s oil industry following Russia’s full-scale invasion of Ukraine in 2022.

In its first report of the tanker drifting in German waters, the CCME said the vessel was 274m (898ft) long and 48m (157ft) wide, carrying about 99,000 tonnes of oil.

German maritime authorities said the oil tanker was drifting at a low speed in the coastal waters of the Baltic Sea, north of the German island of Rügen.

A four-person team of specialists was lowered onto the vessel by helicopter on Friday night to establish towing connections, which were secured. Three tugboats took control of the “stricken vessel” that is “unable to manoeuvre”.

Maritime authorities said on Friday night that no oil leaks had been detected.In its latest update on Saturday afternoon, German maritime authorities said the towing convoy around the tanker was headed to Sassnitz, a town on the island of Rügen.

Earlier, authorities said the convoy of tugboats working to rescue Eventin remained north of Rügen and was moving eastwards “slowly”, at about 2.5 km per hour (1.5mph).

CCME said they had taken safety measures given the rough seas, as the area where the vessel is located was experiencing 2.5m-high (8ft) waves and strengthening wind gusts.

Although the vessel sports the Panamanian flag, German authorities have blamed Russia for the incident.

“Russia is endangering our European security not only with its illegal war of aggression against Ukraine, but also with severed cables, displaced border buoys, disinformation campaigns, GPS jammers and, as we have seen, dilapidated oil tankers,” the German foreign minister said in a statement.Last December, the European Union said it was working on measures including sanctions to target “Russia’s shadow fleet, which threatens security and the environment, while funding Russia’s war budget”.

The European bloc’s remarks came after undersea cables in the Baltic Sea were damaged by a suspected vessel, which the EU believes was part of Russia’s shadow fleet.

The move was a further step taken by Western countries to hit the Kremlin’s oil industry in response to Russia’s full-scale invasion of Ukraine.

Since tougher embargo measures were put in place to halt Russia from exporting oil, Moscow is believed to be using ships with unclear ownership to transport goods – namely oil – across the globe.

As reported by the Atlantic Council, a US-based think tank, Russia is “instrumentalising the dark fleet, using it especially as a primary conveyor of oil exports”.

The shadow fleet, or dark fleet, is the name given to ageing ships that sail “without the industry’s standard Western insurance, have opaque ownership, frequently change their names and flag registrations, and generally operate outside maritime regulations”, according to the Atlantic Council.

The latest incident in the Baltic Sea comes as Washington and London joined efforts to directly sanction energy companies Gazprom Neft and Surgutneftegas.

UK Foreign Secretary David Lammy said the move to weaken Russian oil companies would “drain Russia’s war chest,” adding that funds taken “from Putin’s hands helps save Ukrainian lives”.

But Gazprom Neft slammed the sanctions as “baseless” and “illegitimate”, as reported by Russian state news agencies.

Also on Friday, the US Department of the Treasury said it had sanctioned 183 vessels that are “part of the shadow fleet as well as oil tankers owned by Russia-based fleet operators”.

Video posted on Telegram by Russia’s Southern Transport Prosecutor’s Office, appears to show one of the tankers broken in half and sinking amid a heavy storm, with streaks of oil visible in the water.

At least one crew member is believed to have died – and Russian authorities are investigating for criminal negligence, according to TASS news agency.

The incident took place in the Kerch Strait, which separates Russia from occupied Crimea.

A rescue and clean-up operation is under way involving tugboats, helicopters and more than 50 personnel, TASS news agency reported.

“Today, as a result of a storm in the Black Sea, two tankers, Volgoneft-212 and Volgoneft-239, sank,” Russia’s federal sea and inland water transport agency, Rosmorrechflot, wrote in a statement.

“There were crews of 15 and 14 people on board the ships. The accident resulted in a spill of oil products,” it continued.

Both tankers have a loading capacity of about 4,200 tonnes of oil, Reuters news agency reported.

The full extent of the oil spill remains unclear.

The sanctions are similar to those previously imposed two months ago in response to Iran’s October 1 missile attack on military sites in Israel and to its announced nuclear escalations, the US Department of the Treasury said on Tuesday in a statement.

“Iran continues to funnel revenues from its petroleum trade toward the development of its nuclear program, proliferation of its ballistic missile and unmanned aerial vehicle technology, and sponsorship of its regional terrorist proxies, risking further destabilizing the region,” Acting Undersecretary for Terrorism and Financial Intelligence Bradley Smith said in a statement.

“The United States remains committed to disrupting the shadow fleet of vessels and operators that facilitate these illicit activities, using the full range of our tools and authorities,” Smith added.

Iranian oil and petrochemicals are already under heavy US sanctions.

The Treasury Department’s statement said Iran relied on “a sprawling network of tankers and ship management firms in multiple jurisdictions to transport its petroleum to overseas customers.”

This  includes “tactics such as false documentation, manipulation of vessel tracking systems, and constant changes to the names and flags of vessels.”

The latest sanctions will freeze the entities’ assets in the US and generally make it illegal for Americans to engage in financial transactions with them.

Tehran fired a barrage of missiles at Israel on October 1 in retaliation for the killing of Hamas chief Ismail Haniyeh in Tehran and the assassinations of Hezbollah leader Hassan Nasrallah and an Iranian general in Beirut.

Iran’s envoy to the United Nations, Amir Saeid Iravani, said after the killing of Haniyeh that his country “stands fully prepared to defend its sovereignty and territorial integrity against any aggression targeting its vital interests and security”.

Iran has warned that if an “energy war” were to start, the world would lose about 12 million barrels of oil daily – about 10 percent of global production.