“Mr. Manafort has always denied that he ever received any cash payments for his work and has consistently maintained that he received all of his payments, for services rendered, through wire transfers conducted through the international banking system,” the statement said.

Separately on Wednesday, a spokesman for Mr. Manafort said he had “received formal guidance recently from the authorities” on the need to register, retroactively, for lobbying work in Ukraine, and was “taking appropriate steps in response.” Mr. Manafort was advised last week that he should file the belated registration within 30 days to come into compliance with the law, according to a person with direct knowledge of conversations between Mr. Manafort’s lawyers and the Justice Department.

One of Mr. Manafort’s recent loans, previously unreported, was for $3.5 million in September from the private lending unit of Spruce Capital, a small New York investment firm that has a Ukrainian connection through the billionaire Alexander Rovt. An American citizen who made his fortune in the privatization of the fertilizer industry in post-Soviet Ukraine and has long done business in that part of the world, Mr. Rovt is a financial backer of Spruce, whose co-founder Joshua Crane has been a developer of Trump hotel projects.

Mr. Crane did not respond to requests for comment. Mr. Rovt, who donated $10,000 to Mr. Trump’s campaign on Election Day — the campaign refunded most of it because it was over the legal maximum of $2,700 — said he had never met Mr. Manafort and was not involved in the loan to him. “I did not recommend him or put the parties together,” Mr. Rovt said in an email provided by his lawyer.

Mr. Manafort declined to answer specific questions about any of his loans, other than to say that they “are personal and all reflect arm’s-length transactions at or above market rates.” He derided the interest that his finances had generated in the news media and among do-it-yourself researchers, some of whom have even set up a website that dissects his loans.

“There is nothing out of the ordinary about them,” Mr. Manafort said, “and I am confident anyone who isn’t afflicted with scandal fever will come to the same conclusion.”