The Federal Antimonopoly Service added that the exact amount of fine would be announced on December 24.
The service earlier said Rosneft had "fixed and maintained high monopoly-like prices for gasoline, diesel fuel, jet fuel and fuel oil in the summer of 2008, and also created discriminatory conditions and set different prices for one and the same commodity, which were neither economically nor technologically justified."
According to the service, "LUKoil abused its dominant position on the wholesale market for oil products in the summer of 2008 by fixing monopoly-like high prices for gasoline, diesel fuel, jet fuel and fuel oil."
It concluded that the actions by the oil companies "have given rise to social tension and economic problems in the country."
The Federal Antimonopoly Service fined Gazprom Neft and TNK-BP tens of millions of dollars each in November for abusing their dominant market positions.