Pysaruk, who was deputy governor of the central bank from 2014 to 2015, is now chairman of Raiffeisen Bank Aval, a unit of Austria's Raiffeisen Bank International (RBI).

RBI said in a statement that Pysaruk, who also previously worked at the International Monetary Fund, "was questioned by officials from the National Anti-Corruption Bureau of Ukraine."

"The reason for the action was in no way related to the performance of his duties as Chairman of the Board of Raiffeisen Bank Aval," the Austrian bank said.

RBI Chief Financial Officer Martin Gruell, who heads Raiffeisen Bank Aval's supervisory board, told Reuters that Pysaruk was questioned in relation to the insolvency of VAB Bank when he was deputy governor of the central bank.

RBI said: "We are confident that Mr Pysaruk will be cleared of any suspicion of wrongdoing and that he has always adhered to the highest professional and ethical standards, both at Raiffeisen Bank Aval and for many years at the IMF and other international institutions."

The central bank also issued a statement in support of Pyasruk, saying he was "a professional banker with an impeccable reputation, which has been praised both by the IMF, where he worked for the last three years, and in the international and domestic banking community."

Raiffeisen Bank Aval said Pysaruk would not be commenting and declined to provide his personal contact details to Reuters.

(Reporting by Alexandra Schwarz-Goerlich and Francois Murphy; Additional reporting by Natalia Zinets in Kiev; Editing by Michael Shields and Edmund Blair)