Idemitsu Kosan Co. said Friday it will hike the wholesale prices on its gasoline and other petroleum products in September by 0.50 yen per liter, while Japan Energy Corp. announced a markup of 0.80 yen.

Other large Japanese oil distributors are likely to follow suit to pass on the higher cost of crude oil to retailers, industry observers say.

This month, big petroleum companies raised prices by as much as 10 yen per liter, forcing a spike in prices at the pump.

According to the Oil Information Center, the nationwide average of retail prices for regular gas was 143.9 yen per liter on Aug. 21, surpassing the last high of 142.0 yen in autumn 1990 during the Persian Gulf crisis.