With only a few weeks left before the March Russian presidential election, opposition leader Aleksei Navalny, who has been banned from running, continues his offensive against the Kremlin by exposing ties between oligarchs and Kremlin’s inner circle.

In video released on YouTube on Thursday, Navalny alleges that Russian oligarch Oleg Deripaska acted as a messenger between U.S. President Donald Trump’s ex-campaign chief Paul Manafort and a top Kremlin foreign policy official.

Deripaska denied today all the allegations and called them part of a slander campaign against him. Speaking to the Associated Press by e-mail, a spokesman for Deripaska denounced Navalny’s report, saying it contained “scandalous and mendacious assumptions…driven by sensationalism.”

Oleg Deripaska is a billionaire Russian metals tycoon who has been barred from the United States, and has done business with President Donald Trump’s now-indicted former campaign manager Paul Manafort.

He is also well connected with the Kremlin; Russia’s foreign minister once helped him in efforts to persuade U.S. government officials to grant him a visa.

Published on February 8, Navalny’s exposé allegedly shows a deputy Russian prime minister being lavishly hosted by Deripaska on the tycoon’s yacht off the coast of Norway.

Navalny also said his investigators found public records that said Prikhodko spent several days on Deripaska’s yacht and was flown there on Deripaska’s private jet.

In another video, Deripaska can be heard explaining why relations between the United States and Russia are so tense, something he appears to attribute in part to a former official who used to oversee Russia relations at the State Department and who worked on a Soviet whaling trawler years ago.

In his report, Navalny goes on to claim that Prikhodko’s stay on Deripaska’s yacht effectively amounted to a bribe from the oligarch.

“An oligarch takes a top government official on a ride on his own yacht — that’s a bribe,” Navalny says in the video. “An oligarch pays for all of this, including young women from escort agencies. Believe it or not, this is also a bribe.”

In the 2000s, Deripaska was barred from entering the United States, after the State Department raised questions about possible connections to Russian organized crime groups.

At one point, he enlisted the help of a prominent Washington lobbying firm, and the services of former Republican presidential candidate Bob Dole, in trying to reverse the State Department’s refusal to issue a visa. Congressional lobbying records also show another Washington firm was enlisted by Foreign Minister Sergei Lavrov for help with the visa issue.

Deripaska was also a business partner of Paul Manafort, a former adviser of Dole’s and a longtime Washington lobbyist. In July 2016, Manafort offered private briefings to Deripaska on the Trump campaign’s progress in an email, The Washington Post reported last year.

Deripaska and Manafort signed a contract in early 2006, and records of wire transfers obtained by The Associated Press document million dollar payments to Manafort’s account. This evidence refutes Manafort’s earlier assurances that he worked for Deripaska’s personal businesses, not “representing Russian political interests.”

Manafort was Trump’s campaign manager in 2016 until news about his lobbying work for the Russia-friendly Ukrainian ex-President Viktor Yanukovych emerged. In October 2017, he was indicted by a U.S. grand jury on money laundering, conspiracy, and other charges. He has pleaded not guilty.

Navalny’s investigation alleges that the footage of Deripaska’s yacht meeting with Prikhodko, who served as a foreign policy advisor to Russian leaders for more than two decades, proves the oligarch’s role as a conduit between the Trump campaign and the Kremlin.

Navalny, a charismatic lawyer who rails against corruption, has long been a thorn in the Kremlin’s side. He and his team have published exposés exploring the wealth of Prime Minister Dmitry Medvedev, Defense Minister Sergei Shoigu, Kremlin spokesman Dmitry Peskov, and Prosecutor-General Yury Chaika.

Last year, he released a video examining a Russian island near the Finnish border where a venerable country house has been restored and, he alleged, been used by President Vladimir Putin for holidays.

With witty exposes and sharp-tongued tirades, Navalny has built a national following and become a potent political force in Russia. He garnered substantial votes in the Moscow mayor’s election in 2013, and he had sought to run in next month’s presidential election, challenging Putin.

But election officials have barred him for the race due to an earlier conviction on financial crimes, a charge he and his supporters have called politically motivated.