(Bloomberg) -- A Russian tycoon with former links to the Kremlin has embarked on a $13.8 billion London lawsuit — from a Moscow jail.

Ziyavudin Magomedov, who became a billionaire during Dmitry Medvedev’s four-year term as Russian president, was arrested in 2018 for embezzlement and later handed a 19-year prison sentence. But it hasn’t stopped the businessman from suing private equity firm TPG Inc., as well as a sanctioned pipeline operator Transneft PJSC and state-owned nuclear Rosatom Corp., alleging a vast conspiracy.

In a London filing, Magomedov’s lawyers say the companies, alongside others acting for the Russian state, sought to wrest assets away from him including his stake in the critical commercial port in Vladivostok, which links Russia’s eastern seaboard to Asia.

“The conspiracies form part of a campaign waged against Mr. Magomedov by and on behalf of the Russian state for political reasons,” the tycoon’s lawyer Tim Lord said. “The imprisonment of the Magomedovs is a further part of the same political campaign.”

Magomedov and his brother, Magomed Magomedov, are appealing their convictions. The sentences passed included confiscation orders against all of their assets, according to the filing. 

The Dagestani-born tycoon’s wealth surged during the years when Medvedev held the presidency, in part thanks to state contracts. The size of the claim is worth some $13.8 billion, based on an estimate of the value of Magomedov’s stakes in the various assets. As well as Transneft and Rosatom he’s suing individuals and companies.

Magomedov’s dispute with TPG stems from the private equity firm’s investment in his transportation company Fesco in 2012, which holds the stake in the Vladivostok port. The tycoon alleges that the firm conspired to oust him as part of a plan to clear the path toward exiting its investment.

“We consider these claims, which relate to a legitimate and proper transaction, to be entirely without merit,” a spokesperson for TPG said in a statement. “We intend to defend ourselves vigorously against such allegations.”

TPG said a deal to sell its stake in Fesco back to Magomedov wasn’t completed because the $35 million in funds came from someone unknown to the firm. It finally sold the stake in November 2020.

TPG was previously one of the most active private equity investors in Russia while most rivals steered clear. Founder David Bonderman met with Vladimir Putin in 2009 and joined the supervisory board of VTB after investing in the state-owned-bank. TPG took stakes in supermarket chain Lenta Ltd, a deal that soon turned violent after a disagreement with a shareholder over management. 

TPG is now out of Russia, with no active employees or direct investments. TPG exited the Lenta investment in 2019 when it sold its stake to Russian billionaire Alexey Mordashov, and closed the Moscow office.

Transneft declined to comment. Rosatom didn’t respond.

--With assistance from Olga Tanas.

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