Iranian Oil Ministry announced that oil exports to Japan had been on the rise during three consecutive months to reach 257,000 barrels per day (bpd) in July.
This indicates a 62-percent increase compared to the figure for the same month last year, IRNA reported.
The latest figures also show that Iran's main oil customers in East Asian were China, South Korea and Japan. Their average imports stood at 1.64 million barrels per day and the figure is on the rise.
Since the beginning of 2016, Japan's crude import from Iran has reached 213,000 bpd, showing a 42,000-bpd increase against the figure for the same period of the previous year.
Meanwhile, Japan's crude imports from Saudi Arabia reached 1.61 million bpd in July, indicating a 70,000-bpd decrease compared to the figure for the same month last year.
Japan was one of the key clients of Iranian oil with 338,000 bpd of imports prior to the Western sanctions on Iran in 2012. During the years of sanctions, the Asian country continued to import crude from Iran, though at limited volumes, under a preliminary nuclear agreement.
Iran hosted several leading Japanese companies in its oil and gas projects before the sanctions were imposed.
After the removal of sanctions, Asian imports of Iranian oil have risen sharply. Iran's oil flows to Europe have also begun to pick up after a slow start.
The surge in Iran's oil exports points to Iran's success in regaining market share after the sanctions were eased in January.