Figures released by Reuters showed that South Korea’s imports of oil from Iran over the period stood at below 180,000 barrels per day (bpd).
The decline was mainly attributed to lower production of condensate – an ultra light fuel – by Iran.
As a result, the cumulative import decline for the first five months of the year came in at 33 percent to 5.45 million tons, Reuters added.
Imports from Saudi Arabia also declined in May, by 23.6 percent to 763,620 bpd.
Saudi Arabia is South Korea’s largest crude supplier.
While Iranian and Saudi imports declined, shipments from the United States and Russia increased. Imports from the US rose threefold to 95,800 bpd, and imports from Russia jumped 78 percent to 218,165 bpd, the report added.
South Korea is the world’s fifth-largest crude oil importer, and diversity of supplies is vital. The last time there were sanctions against Iran, South Korea managed to score a waiver by pledging to cut the amount of crude it buys from Tehran.