A Ukrainian MP has divulged details of what he said were payments made to Donald Trump's campaign chief by the political party of the Kremlin-backed former Ukrainian leader Viktor Yanukovich.
MP Serhiy Leshchenko said money was allocated for Trump aide Paul Manafort to finance services such as carrying out exit polls at elections, buying computers and conducting research.
The largest single payment was US$3.5 million ($4.81 million).
Manafort has denied allegations - first made in the New York Times on Monday (US time) - that he received cash payments worth more than US$12 million over five years that were itemised on secret ledgers belonging to Yanukovich's Party of Regions.
Ukrainian anti-corruption investigators have corroborated the existence of what they called a "black ledger" of payments made by Yanukovich's party but stressed that they could not establish whether Manafort himself received money.
Leshchenko, a member of President Petro Poroshenko's parliamentary faction, called on Ukrainian authorities to send a request for assistance to Washington to investigate Manafort.
"Manafort didn't work for free in Ukraine, he served the Party of Regions for over 10 years and it is clear that his work was paid," Leshchenko told a news conference.
"The money was transferred in cash and it is impossible to trace the transactions, but I have no doubt as to the authenticity of these documents," he said.
"If Mr Manafort denies any allegations, I think he has to be interrogated into this case and prove his position that he was not involved," Leshchenko added.
Democratic presidential candidate Hillary Clinton's campaign has previously said the allegations were evidence of "more troubling connections between Donald Trump's team and pro-Kremlin elements in Ukraine".
Trump, a Republican, has spoken favourably in the past of Russian President Vladimir Putin. Last month, he invited Russian hackers to find "missing" emails from Clinton's time as secretary of state, when she used a private email server to conduct government business, although he later described that call as sarcasm.
In response to the earlier report in the New York Times, Manafort denied any impropriety in a statement on Monday.
"I have never received a single 'off-the-books cash payment' as falsely 'reported' by The New York Times, nor have I ever done work for the governments of Ukraine or Russia," he said.
Trump overhauled his top political team this week, demoting Manafort, who was brought on as campaign chief in June to professionalise its approach but struggled to get the wealthy businessman to rein in his freewheeling ways.