Ukrainian oligarch Dmytro Firtash, who has been accused of links to the Russian mob, has lost his gas empire, according to the chief of Ukrainian state energy giant Naftogaz.

"Deoligarchization. This term was talked about a lot in the gas market, but here in Ukraine, the group of [oligarchs] Firtash [led] for almost two decades had dominated. Now, this is coming to an end," Naftogaz CEO Yuriy Vitrenko said at a press briefing on Tuesday.

Vitrenko said that currently, nearly all household consumers—or 97.6 percent—receive gas from Naftogaz directly, making the company a monopoly in Ukraine's retail gas market.

"There is no intermediary between us in the form of the Firtash group, which has never been a real supplier, but was an intermediary who did not bear the risks that real suppliers usually bear, in the European sense of the word," he said.

A group led by Ukrainian oligarch Dmytro Firtash will no longer dominate the country's gas market. Pictured, Firtash prior to a public hearing at the higher regional court in Vienna on February 21, 2017. Firtash, one of Ukraine's richest men and previously an ally of ousted president Viktor Yanukovych, was arrested in Austria in March 2014.GEORGES SCHNEIDER/PHOTONEWS.AT/AFP/Getty Images

Vitrenko told reporters that Firtash's regional gas companies will soon move to Naftogaz.

"[Naftogaz] will actually have more than 60 percent in this gas distribution or transportation market," he said.

The billionaire, with reported links to the Kremlin, is sanctioned in Ukraine for selling titanium products that allegedly end up being used by Russian military enterprises.

He has also been indicted in the U.S. on racketeering and bribery charges. Firtash has denied wrongdoing and has fought extradition from Vienna.

In April, Firtash denounced Russian President Vladimir Putin in an interview with NBC News while under house arrest in Austria, by saying that he believes the Russian president will lose his war against Ukraine, which began in late February.

"He is never going to come out victorious," said Firtash. "No matter what happens, Russia will lose."

Firtash said he would tell Putin that it's "time to stop" and that "there will be no victory."

"The longer this war takes, the worse it will be for the Russian people. Not just for the Ukrainian people," he said.

"I was never pro-Russian," Firtash said. "But you have to understand that I am a businessman. And my goal is to earn money. That's my job."

The Ukrainian oligarch called Putin's war "a massacre."

"To believe that in 2022, in the center of Europe, that such a massacre can be taking place, no normal person could believe it," he said.

According to State Department cables made public by WikiLeaks, Firtash told U.S. officials that he acknowledged needing, and receiving, permission from Semion Mogilevich in 2002, when he established various businesses. At the time, Mogilevich was considered by American officials one of the most dangerous Russian mobsters in the world.

Firtash's spokesman Lanny Davis told NBC News that the businessman "denied any business or other relationship with Russian organized crime," and denied being "used by the Russians" or acting "on behalf of the Kremlin."

Correction 6/22/22, 10:36 a.m. ET: This article has been amended to state that Firtash has denied wrongdoing and has fought extradition from Vienna, not Vitrenko.