In the race to seize assets tied to sanctioned Russian billionaires, U.S. authorities are alleging that a Russian tycoon acted as the ¡°straw owner¡± of two yachts worth more than $1 billion, including the $700 million Scheherazade, a superyacht linked to Russian President Vladimir Putin.

Court filings in the South Pacific island of Fiji, where the U.S. is trying to seize the $325 million yacht Amadea, reveal what U.S. officials allege is a nest of offshore shell companies that were set up with the help of a yacht broker to conceal the true owners of both vessels ¡ª an allegation that lawyers for the listed owner and the broker dispute. A hearing is scheduled for Wednesday in Fiji on the fate of Amadea.

The layers of companies and trusts, stretching from the Marshall Islands to Switzerland, indicate the beneficial owner of both yachts is the former president of state-controlled Rosneft OJSC, Eduard Khudainatov, according to the documents. Khudainatov doesn¡¯t appear on any sanctions lists. But the U.S. alleges the ¡°true beneficial owner¡± of the 348-foot Amadea, which features a helipad, a mosaic-tiled pool and a lobster tank, is Russian gold billionaire Suleiman Kerimov, who was first sanctioned by Washington in 2018.

¡°The fact that Khudainatov is being held out as the owner of two of the largest superyachts on record, both linked to sanctioned individuals, suggests that Khudainatov is being used as a clean, unsanctioned straw owner to conceal the true beneficial owners of these vessels,¡± according to an affidavit by a special agent with the U.S. Federal Bureau of Investigation, filed in the Fiji court proceedings. ¡°While Khudainatov is wealthy, there is no reason to believe he has the financial resources to purchase both the Amadea and the Scheherazade, which are collectively worth more than $1 billion.¡±

That April 22 affidavit, which Bloomberg News has reviewed, reveals previously redacted details from a U.S. seizure warrant for Amadea that was filed in federal court in Washington. It describes interviews with rival yacht brokers, crew members and emails, presented as evidence that Amadea is really owned by the 56-year-old Kerimov, who is worth $15.6 billion, according to the Bloomberg Billionaires Index. His family held a stake in Polyus, Russia¡¯s largest gold miner. A lawyer for Kerimov and a Polyus spokesperson did not respond to requests for comment. A lawyer for Amadea¡¯s registered owner has written that the U.S. effort to seize the yacht is based on hearsay evidence that doesn¡¯t prove Amadea¡¯s true owner is Kerimov.

The U.S. affidavit cites evidence that Kerimov family members requested long-term changes to Amadea consistent with owning, rather than renting it. They were involved in approving the installation of a new pizza...