The US Treasury Department has blacklisted the ship management affiliate of Saint Petersburg-headquartered tanker giant Sovcomflot (SCF Group) as it ratcheted up enforcement of the price cap on Russian oil.

US officials also added a raft of what they described as “under-the-radar traders” in a bid to put pressure on intermediaries helping to move Russian oil days after G7 leaders committed to tightening compliance with the price cap sanctions.

The Treasury Department’s addition of Sun Ship Management to the sanctions backlist maintained by the Office of Foreign Asset Control (Ofac) is Washington’s hardest blow yet against Sovcomflot.

Individual Sovcomflot ships and registered owners have been sanctioned since Russia invaded Ukraine last year, and US officials have put restrictions on providing finance to the shipping giant, but Dubai-based Sun Ship has some 24 vessels under management, according to Equasis data.

The move by the US comes after sanctions by the UK and European Union against Sun Ships.

The Treasury Department cited Sun Ship’s management of the 157,300-dwt suezmax SCF Primorye (built 2009), which Ofac blacklisted in October for carrying oil above the $60-per-barrel cap that sanctions place on Russian crude while it was “using services of a covered US provider”.

TradeWinds reported on Monday that Liberia, whose shipping registry is managed by a US company, is de-flagging seven tankers blacklisted by the US. Equasis data shows that the SCF Primorye switched from the Liberian flag to Russia on 1 December.

Ships listed under the management of Sun Ships fly the flags of Panama and Liberia.

Press representatives at Sovomflot could not be immediately reached for this story.

Deputy treasury secretary Wally Adeyemo said the latest blacklistings demonstrate Washington’s commitment to the price cap policy.

“Participants in the maritime transport of Russian oil, especially Tier 1 actors like traders, must adhere to the compliance guidelines agreed upon by the Price Cap Coalition or face the consequences,” he said, referring to the tier of market actors that are held to the highest compliance expectations.

Ofac placed three international trading companies on its blacklist, officially known as the Specially Designated Nationals list.

Officials said vessels by Hong Kong-based Bellatrix Energy carried out more than 150 port calls in Russia.

Also based in Hong Kong, Covart Energy is accused of carrying out at least 23 port calls in Russia with chartered vessels, including three that have been identified by Ofac as carrying crude sold above the price cap.

Treasury also blacklisted the 7,005-dwt product tanker Sanar 15 (built 2015), which is owned by Covart.

Also added to the blacklist was United Arab Emirates-based Volition DMCC, which has made at least eight port calls in Russia since the price cap went into effect.

TradeWinds could not immediately reach the trading companies for comment.