A former head of Ukraine's state-owned oil and gas company Naftogaz is suspected of embezzling the equivalent of around $10 million, the National Anti-Corruption Bureau of Ukraine said on Jan. 19.

The person under suspicion was "the Naftogaz CEO (2014-2021)," the agency said in a statement.

It said it had notified the individual that he was suspected of illegally awarding himself a bonus in 2018 "for extraordinary achievements."

Andriy Kobolyev, who was chairman and CEO of the company during that time, said in a Facebook post that he had returned to Ukraine from a trip abroad after learning that the investigation was being prepared in order to avoid a perception that he had fled.

"I am definitely not planning to do this [flee] but am planning to prove my innocence," he wrote.

He has denied any wrongdoing by Naftogaz officials during his administration.

Kobolyev was dismissed from Naftogaz abruptly in 2021, a move which drew scrutiny from the United States and prompted the resignation of its supervisory board.

Anti-corruption authorities in Ukraine, which was invaded by Russia in February last year, have in recent months stepped up their fight against graft.