The seizure of a Russian-linked oil tanker in the North Atlantic has highlighted “worry” among NATO and Nordic-Baltic governments over dark fleet vessels and the type of crews onboard, according to a maritime intelligence analyst.

U.S. military and Coast Guard personnel boarded the Marinera between Iceland and the U.K. Wednesday as it operated under deceptive shipping practices, including flying a false flag and violating sanctions.

According to Reuters, Russian authorities demanded the humane treatment and repatriation of the crew members.

Windward maritime intelligence analyst Michelle Wiese Bockmann claimed the Marinera’s ownership had just been transferred to Burevestmarin LLC, a Russian company.

TREASURY TARGETS OIL TRADERS, TANKERS ACCUSED OF HELPING MADURO EVADE U.S. SANCTIONS

“We do not know the status of these sailors and seafarers, who are Russian nationals,” Wiese Bockmann told Fox News Digital. “That lack of clarity is common 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.”

WORLD’S BIGGEST OIL RESERVE HOLDER FACES US CHOKEHOLD AS TRUMP TARGETS VENEZUELA’S SHADOW TANKER FLEET

“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.

US COAST GUARD PURSUES THIRD ‘DARK FLEET’ OIL TANKER AS TRUMP TARGETS VENEZUELAN SANCTIONS EVASION NETWORK

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.

CLICK HERE TO DOWNLOAD THE FOX NEWS APP

“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.