Washington (CNN)A Russian oligarch who was questioned by special counsel Robert Mueller and recently sanctioned by the US visited President Donald Trump's personal attorney Michael Cohen in Trump Tower during the presidential transition in January 2017, according to video reviewed by CNN and a person familiar with the matter.

The January 9, 2017, Trump Tower appearance by Viktor Vekselberg, which was also reported Friday by The New York Times, adds to the questions swirling over the payments to Cohen, which Mueller's team questioned Vekselberg about after the FBI stopped his private jet at a New York-area airport earlier this year.

Vekselberg, chairman of Russian asset manager Renova Group, was accompanied at Trump Tower by Andrew Intrater, who is Vekselberg's cousin and head of Columbus Nova. Vekselberg is Columbus Nova's biggest client.

A person familiar with the meeting told CNN that Vekselberg and Intrater met with Cohen and discussed improving US-Russia relations. The meeting was brief, the person said, and Vekselberg was not originally expected to attend.