KIEV, June 15 - UkrTatNafta, Ukraine's largest oil refinery, majority controlled by Russian regional oil company Tatneft, may be fined for overcharging clients while selling jet fuel, the country's anti-cartel agency said Friday.

"We believe they have increased jet fuel prices without sufficient reason," Oleksiy Kostusev, the head of the Anti-Monopoly Committee, said at a press conference.