The recent capture of an oil tanker with Russian connections in the North Atlantic has stirred concern among NATO and Nordic-Baltic nations. This incident underscores growing apprehensions about so-called “dark fleet” vessels and the nature of their crews, says a maritime intelligence expert.

In a bold operation, U.S. military and Coast Guard forces boarded the tanker Marinera on Wednesday. The vessel was intercepted between Iceland and the U.K. while engaging in deceptive maritime practices, such as flying a false flag and breaching international sanctions.

Following the incident, Russian officials issued a statement demanding that the crew be treated humanely and that arrangements for their return be made promptly, as reported by Reuters.

According to Michelle Wiese Bockmann, a maritime intelligence analyst at Windward, the Marinera’s ownership was recently transferred to a Russian firm, Burevestmarin LLC.

The U.S. military confirmed the seizure of the Marinera, which was flying a Russian flag, in the North Atlantic on January 7, 2026. This information was released by the U.S. European Command.

“We remain uncertain about the conditions faced by these Russian sailors and crew members,” Wiese Bockmann explained to Fox News Digital. “Such ambiguity is typical with dark fleet tankers.”

“The Marinera did have its ownership transferred to a newly formed Russian company, with the registered owner, ship manager and commercial manager being Burevestmarin LLC.”

She also suggested NATO and the Nordic-Baltic 8+ group of governments have been “worried” about sanctioned oil tankers with unauthorized personnel onboard, including “armed guards.”

U.S. forces seized the Russian-flagged Marinera oil tanker in the North Atlantic Sea Wednesday, Jan. 7, 2026, according to the U.S. military. (US European Command)

“Increasingly, and I know the Nordic Baltic 8+ governments are worried about the fact that you are having unauthorized people also on board, also known as armed guards,” Wiese Bockmann said. “But it is highly irregular.

“Armed guards are rarely seen and typically used on ships that are transiting the Gulf of Aden or the Red Sea and are therefore assessed as at risk from attack by Houthis or pirates,” she added.

After the seizure, White House press secretary Karoline Leavitt rejected Russian demands for special treatment of the Marinera’s crew during her regular briefing Wednesday.

“This was a Venezuelan shadow fleet vessel that had transported sanctioned oil,” Leavitt said.

“The vessel was deemed stateless after flying a false flag, and it had a judicial seizure order. And that’s why the crew will be subject to prosecution.”

Russia’s Foreign Ministry said it was “closely following” the situation, according to the state-run TASS news agency.

A crude oil tanker waits its turn to be loaded with crude oil at Lake Maracaibo in Maracaibo, Zulia State, Venezuela, May 9, 2025.  (Federico Parra/AFP/Getty Images)

Wiese Bockmann noted that dark fleet crews are often multinational, typically involving a Russian master with Chinese, Indian or Filipino crew members.

“There is a blurring of commercial and military shipping around the dark fleet,” she said. “What we’re seeing now is something that has really only emerged in the last six or seven months.”

European authorities have also begun holding crews accountable, particularly when captains are “facilitating dangerous deceptive shipping practices, such as spoofing and going dark,” she explained.

“The EU recently sanctioned the captain of a tanker who refused orders from the Estonian navy (Jaguar) to be stopped for inspection last May. And the French charged a captain over his refusal to comply with orders and failure to justify a flag’s nationality after authorities intercepted a dark fleet tanker in the Atlantic last October,” Wiese Bockmann added.

As previously reported by Fox News Digital, a second vessel, the M. Sophia, was also boarded in international waters near the Caribbean while en route to Venezuela.

Fox News Digital has reached out to the White House for comment.