The Russian metal tycoon alleges that the two men failed to "explain what had happened" to his hefty investment and intentionally concealed

Oleg Deripaska alleged in a lawsuit filed Wednesday that Manafort and Gates "vanished more than $18.9 million" that he had invested through his business, Cyprus-based Surf Horizon Ltd., "in a purchase they recommended of Ukrainian cable and internet companies," according to the complaint

A billionaire Russian businessman is suing former Trump campaign chairmanand his partner Richard Gates for fraud, alleging that they misappropriated millions of his funds in the late 2000s.

"In response to a federal court subpoena, neither Manafort, nor Gates, provided any documents showing how Surf's $26 million actually had been spent or what happened to its investment. Indeed, during their depositions they testified falsely that they did not possess or have any control over such documents," Deripaska's lawyers wrote.

Deripaska, who filed his lawsuit in the New York state court, is seeking $25 million in "compensatory damages" and "punitive damages" from Manafort and Gates.

Manafort's spokesman expressed surprise at the lawsuit, stating that they believed the matter had already been settled.

“We are surprised by this filing. This is a commercial matter which we thought had been addressed and resolved years ago. We will respond, if we must do so, in the appropriate manner,” Manafort's spokesman, Jason Maloni, said in a Thursday statement to The Hill.

A spokesman for Deripaska’s investment group indicated that new "evidence" prompted them to take legal action.

“It was only in the past year that Surf obtained access to evidence showing that, not only had Messrs. Manafort and Gates failed properly to supervise the investment, but each had secretly and improperly profited from it,” a spokesman for Deripaska’s investment group told The Wall Street Journal in a statement.

A lawyer for Gates did not immediately respond to a request for comment.

The lawsuit comes at a time when a federal and multiple congressional investigations are looking into the Trump campaign's ties to the Kremlin.

Manafort's business ties to Russia have come under immense scrutiny. His multi-million dollar connection to Deripaska is another previous business dealing that has captured the attention of investigators.

In October, Mueller indicted Manafort and Gates on 12 counts including conspiracy against the U.S. and using laundered money to buy goods in the U.S. — charges that relate to his work on behalf of a pro-Russia political party in Ukraine. The indictment does not point to any of Manafort’s work for Trump’s campaign, which took place between March of 2016 until his ouster in August.

Both Manafort and Gates pleaded not guilty to all the charges from Mueller's probe.

Mueller's indictment helped Deripaska's case by providing "detail regarding the movement of funds from bank accounts in Cyprus to accounts in the United States controlled by Manafort and Gates,” the court complaint says.

When a financial crisis struck, Deripaska requested that they sell Black Sea Cable, and despite repeatedly indicating that they were looking for a buyer, Manafort and Gates “took no steps to find a buyer for Black Sea Cable,” the complaint says.