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.
The decline in the country’s imports of Iranian oil occurred before US President Donald Trump announced that he would re-impose sanctions on the Islamic Republic, Reuters wrote.
Trump’s announcement in May came when he said he would pull the US out of a 2015 nuclear agreement with Iran that restricted Iran's nuclear program in exchange for the removal of sanctions.
The US president had already emphasized that the regime of sanctions he plans to impose on Iran will be “at the highest level”.
The sanctions would include a universal ban on Iran over buying or acquiring US dollars as well as restrictions over purchases of crude oil from the country and investing in its oil sector projects.
Meanwhile, other media highlighted South Korea’s concern about the impacts of upcoming US sanctions on its plans to import oil from Iran.
To the same effect, Platts news service quoted Ali Kardor, the managing director of the National Iranian Oil Company (NIOC), as saying that Seoul was worried about sanctions on tankers since “they didn't have their own shipping and were outsourcing, like charter, so maybe that is why the issue. But we told them that our ships are ready for you."