China, India, Japan and South Korea last month imported 1.8 million barrels per day (mbd) from Iran, the data showed. That was nearly 15 percent higher than a year earlier and the most since September, Reuters reported.
China's imports of Iranian crude in May rose 5.3 percent to just over 718,000 bpd from the previous year and are almost 10 percent higher in the first five months of the year.
India's imports from Iran jumped nearly 45 percent from May last year to around 700,000 bpd and are up 6.4 percent in the year through last month.
South Korean purchases slumped 27 percent to nearly 194,000 bpd and fell by more than a third in the year to date.
Imports into Japan rose 32 percent in May to around 210,000 bpd from a year earlier, but are down five percent for the year, data from the country's Ministry of Economy, Trade and Industry showed on Friday.