The average retail price of regular gasoline rose ¥1.0 from a week earlier to ¥168.4 per liter as of Monday, up for the 10th straight week, the Natural Resources and Energy Agency said Wednesday.
Gasoline prices rose in 46 of the 47 prefectures. Only in Kochi did the price remain flat.
Excluding the rise on the April 1 consumption tax hike, it was the first time in about a year that the average price increased as much as ¥1.0, according to the Oil Information Center, which conducts the survey on behalf of the agency.
The per-liter price was highest in Kagoshima Prefecture, at ¥175.8, and exceeded ¥170 in Tokyo, Nagano, Shizuoka, Kyoto and seven other prefectures.
The biggest jump in price was ¥2.8 in Ishikawa, followed by ¥2.5 in Toyama.
The escalating Iraqi crisis has pushed up gasoline prices to their highest levels in five years and nine months in recent weeks, an official of the center said, adding pump prices are unlikely to come down for the time being.