Officers from the National Anti-Corruption Bureau of Ukraine (NABU) are conducting searches in the Kyiv office of PJSC Ukrnafta, the oil company reported on its Facebook page.

"The search is being conducted in accordance with the decision of Solomiansky court within the pre-trial investigation, which has been conducted since November 2015. We cooperate with the investigators and provide all the necessary documents," the report said.

Ukrnafta is the country's largest oil producer. Naftogaz Ukrainy owns a 50% plus one share stake in Ukrnafta, a group of companies associated with the former shareholders of PrivatBank holds about 42% of the shares.