They include payments in 2007 and 2009, providing the first evidence that Manafort's firm received at least some money listed in the so-called Black Ledger, The Associated Press reports.

The two payments came years before Manafort became involved in Trump's campaign, but for the first time bolster the credibility of the ledger. They also put the ledger in a new light, as federal prosecutors in the U.S. have been investigating Manafort's work in Eastern Europe as part of a larger anti-corruption probe.

Read alsoU.S. agents have obtained documents on Paul Manafort in eastern Europe inquiryUNIAN memo. According to the investigation by The New York Times, former head of Trump campaign Manafort could receive $12.7 million from the "black ledgers" of the Party of Regions, at the times of his cooperation with Viktor Yanukovych. Before joining Trump's election campaign, Manafort’s most prominent client was ex-President of Ukraine Vitkor Yanukovych. Manafort played the role of political adviser and advisor, eventually helped the Party of Regions and Yanukovych win several election campaigns in Ukraine.

In December 2016, Manafort claimed that the "black ledgers" of the Party of Regions were falsified.

Also last year, head of the National Anti-Corruption Bureau of Ukraine Artem Sytnik said that the bureau was investigating into the ledgers of the Party of Regions, at the same time refuting reports on NABU probing Manafort personally.