In the five-year period from 2007 to 2012, Manafort was paid at least $12.7 million, according to a handwritten Party of Regions ledger found later in its head office, Bloomberg reported.

Ukraine's anti-corruption bureau and the FBI are investigating whether the ledger reflected any illegal payments to Manafort and to others. Manafort's spokesman says that after being paid he had many expenses and so the payment figure does not represent profit. One payment to Manafort on the ledger matches an invoice he signed in 2009 to sell $750,000 of computers to a Belize-registered company called Neocom Systems Ltd., according to documents obtained by Ukrainian MP Leshchenko from Manafort's Kyiv office.

Read alsoManafort falsified invoice to Belize company to legitimize Yanukovych's $750,000 payment to himself – Ukrainian MPDoug Singh, who runs International Corporate Services (ICS), which registered Neocom in 2007, says he's received multiple requests for records from Belize's Financial Intelligence Unit, which investigates money laundering.

Belize authorities declined further comment. Evgeniy Kaseev, listed as a director of Neocom, couldn't be reached for comment.

Manafort's spokesman disputed the authenticity of the invoice and said Manafort is unfamiliar with it.

UNIAN 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.