Russian opposition leader Alexei Navalny at a rally in Moscow on Jan. 28. (Evgeny Feldman/AP)

Russian opposition politician Alexei Navalny published a video Thursday in which he accuses one of Russia’s richest men of bribing a top government official by entertaining him on his yacht with several women described as escorts.

In the video posted to YouTube, Navalny says that his team of anti-corruption activists unearthed Instagram posts by a woman who said she worked for an escort agency and claimed to have been romantically involved with billionaire Oleg Deripaska. The Instagram posts appear to show the aluminum tycoon relaxing on a yacht in Norway in 2016.

In several videos, Deripaska appears to be joined by at least one other woman, as well as by Sergei Prikhodko — a deputy prime minister in the Russian government.

“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.”

Navalny said his team verified the woman’s posts by checking public records for boats and private planes. Navalny said the woman wrote a book about the experience, using pseudonyms for Deripaska and Prikhodko, titled, “A Diary About Seducing a Billionaire.”

After Navalny’s investigation was published, the woman, who goes by the name Nastya Rybka, posted a new video on Instagram in which she said that what took place on the yacht “was in truth a gang rape.”

A spokesman for Deripaska on Thursday slammed the report and denied the accusations. “These scandalous and mendacious assumptions are driven by sensationalism and we totally refute these outrageous false allegations in the strongest possible way,” the spokesman told the Associated Press in a statement.

The investigation by Navalny, whom Russian authorities banned from running against Vladimir Putin in the March 18 presidential election, underscores his ability to use Russia’s still-open Internet to get attention despite the government’s crackdown on free speech elsewhere. While Russia's mainstream media largely ignored Navalny’s report, his video drew some 700,000 views on YouTube within hours. Navalny is now trying to use his social media reach to try to persuade Russians to boycott the March election, in which Putin is expected to win a fourth term.

Deripaska has been linked to former Donald Trump campaign chairman Paul Manafort, a key figure in U.S. special counsel Robert S. Mueller III’s probe into Russia’s meddling in the 2016 U.S. presidential election. In October, Manafort was indicted on charges of conspiracy and money laundering, the first disclosed charges in that investigation.

According to emails described to The Washington Post last year, Manafort  — who once worked for Deripaska — directed an associate to offer Deripaska “private briefings” about Trump’s presidential campaign. A Deripaska spokeswoman said he was never offered such briefings.

What you need to know about Paul Manafort's ties to Russia. (Thomas Johnson/The Washington Post)