Gasoline prices at the pump in Japan have risen for the fourth straight week, hitting the highest level in about 13 years, despite emergency measures to stem the rise.

The Oil Information Center says the average retail price of regular gasoline nationwide was 170.9 yen, or one dollar and 49 cents, per liter as of Monday. That was up 0.4 percent from the week earlier.

The industry ministry started providing a subsidy to oil wholesalers last week, after the average price topped the government-set threshold of 170 yen.

Officials say the measure brought down the price by 2.5 yen, or 2 cents. But they say it will probably take a week or two before the effects of the subsidy are fully reflected in the retail prices.