Nippon Oil Corp. and other major oil companies raised wholesale prices of gasoline and other petroleum products Tuesday by 4 yen to 10 yen per liter from last month, primarily because of higher costs of crude oil.

Retail prices were also raised nationwide, with regular gasoline rising to the 140 yen per liter level at most gas stations in greater Tokyo.

The average retail price of regular gas nationwide was 137 yen per liter as of July 24, the Oil Information Center said.

If higher wholesale prices continue to be passed on to retail prices, the average retail price could top the record 142 yen set in fall 1990 during the Persian Gulf War.

In addition to Nippon Oil, Idemitsu Kosan Co., Japan Energy Corp. and Showa Shell Sekiyu K.K. were among those that raised wholesale prices Tuesday. Exxon Mobile Corp. raised them Saturday.

At a gas station in Shinagawa Ward, Tokyo, run by a sales subsidiary of Nippon Oil, the price of regular gasoline was raised Saturday from 139 yen per liter to 146 yen before the hike in wholesale prices.

"I think our customers understand the situation because the move to increase prices had already been reported by the media," said Isao Maruyama, head of the Nippon Oil filling station. "Our business was at the end of its rope recently because we could not pass the cost hikes on to prices."