A luxury superyacht taken from a sanctioned Russian oligarch has been sold to an undisclosed buyer for $37.5m (£35m) in the first sale of its kind since Russia invaded Ukraine.

The 72.5-metre Axioma was seized from the steel billionaire Dmitry Pumpyansky in March following sanctions by the UK, EU and US.

However, the yacht which features a swimming pool, a 3D cinema room, a gym, a jacuzzi and a fully equipped spa, was not sold for the benefit of the Ukrainian people but for a US investment bank, JP Morgan, which claims Pumpyansky owes it €20.5m.

The yacht was impounded by the Gibraltar authorities in March, following a court claim from JP Morgan. The Office of the Admiralty Marshal, a branch of Gibraltar’s supreme court, oversaw an auction of the yacht in August, which attracted 63 bids.

“The Admiralty Marshal has today sold the MY Axioma following payment into court of US$ 37,500,055 by the successful bidder,” the court said in a statement on Tuesday. “The bid was selected after completion of an enhanced due diligence process, but the Admiralty Marshal will not be disclosing the identity of the buyer.”

Pumpyansky was until March of this year the owner and chairman of the steel pipe manufacturer OAO TMK, a supplier to the Russian state-owned energy company Gazprom. The UK said the billionaire, who it said had built up an estimated £1.84bn fortune, was one of the oligarchs “closest to Putin”.

The yacht was detained by the Gibraltar government after a legal claim from JP Morgan, which said Pumpyansky’s holding company Pyrene Investments owed it €20.5m.

JP Morgan said the fact the billionaire had been subjected to sanctions meant the terms of the loan had been breached because it legally could not accept repayments from Pyrene, and asked the Gibraltar courts to detain and sell the yacht.

The yacht, the work of the superyacht designer Alberto Pinto, was built by Dunya Yachts in Turkey in 2013. The boat, which was originally named Red Square before being renamed Axioma, was available for other millionaires to charter for $558,500 a week.