A Russian-born, mafia-linked businessman whose ties to both Donald Trump and loyalists of Russian President Vladimir Putin have sparked scrutiny, visited Trump Tower last month for undisclosed business, he told POLITICO.

The businessman, Felix Sater, also donated the maximum allowable contribution to Trump’s presidential campaign, according to the campaign’s most recent FEC filing.

Sater, whose firm co-developed a major Trump project in New York and who was later hired by Trump to drum up business in the former USSR, has said that he closely associated with Trump and his family, while Trump has suggested he wouldn’t even recognize Sater.

Sater told POLITICO that he has not seen the candidate recently and that the purpose of his visit to Trump Tower last month is “confidential.” Sater declined to say whether he’s had recent contact with the Trump Organization or Trump’s children. “I don’t see the relevance of that,” he said.