New figures show Irans oil exports to Japan increased by more than 28 percent in October compared with the same period last year.
According to the data released by Japans Ministry of Economy, Trade and Industry on Friday, the worlds third-biggest economy imported 163,288 barrels per day (bpd) of Iranian crude during the period.
India, Iran's top oil client after China, also imported about 309,900 bpd of crude from Tehran last month.
The data show that Indias oil imports from Iran rose 60 percent in October year on year.
Irans oil exports have increased this year partly due to the interim nuclear deal signed between Tehran and six world powers in November 2013.
The interim accord has provided Iran with some sanctions relief in exchange for the country having agreed to limit certain aspects of its civilian nuclear work. Part of the sanctions targeted the Islamic Republics oil and financial sector.
Irans total in-place oil reserves have been estimated at more than 560 billion barrels, with about 140 billion barrels of recoverable oil. Heavy and extra heavy varieties of crude oil account for roughly 70-100 billion barrels of the total reserves.
Foreign oil giants have expressed interest in returning to Irans projects as sanctions targeting the Islamic Republics energy sector are widely hoped to be eased as a result of Tehrans nuclear talks with six world powers for a final accord.