KIEV, July 10 – Ukraine’s national oil and gas company, Naftogaz Ukrayiny, said Tuesday it had won a shareholder dispute with Russian oil company Tatneft and now controls a majority stake in the country’s largest oil refinery, UkrTatNafta.

The development suggests that the dispute between Naftogaz and Tatneft has escalated sharply and may potentially lead to disruptions of crude oil supplies to the refinery.