Reuters - South Korea's Iranian crude oil imports dropped in May to their lowest in eight months as refiners bought less of the Middle Eastern nation's condensate, while Tehran struggled to maintain shipment volumes after exhausting stocks stored on tankers.

South Korea's Iranian crude intake fell 18.7 percent in May from a year ago to 1.02 million tonnes, or 242,058 barrels per day (bpd), customs data showed on Thursday. That was the lowest since last October when Seoul imported 902,987 tonnes.

South Korea's crude imports data includes an ultra-light oil known as condensate, but a breakdown is not available.

"South Korean buyers purchased less condensate from Iran because of high prices and diversified condensate import sources," said a spokesman at SK Innovation, owner of South Korea's top refiner SK Energy.

South Korea imports condensate mainly from Iran and Qatar.

Iran, a member of the Organization of the Petroleum Exporting Countries (OPEC), is exempt from that group's drive to curb oil supply to boost prices, pushing to regain market share lost during years of sanctions over its nuclear programme.

But it has already used up oil stocks it had in floating storage - mostly made up of condensate - and it is now fighting to boost crude output to support export volumes.

Iran's crude exports were set to fall to a 14-month low in May, a person with knowledge of Tehran's loading schedules told Reuters in April.

South Korea, one of Iran's major Asian customers, took in 8.12 million tonnes of its crude, or 394,324 bpd, over the January-May period. That was up nearly 60 percent from 5.08 million tonnes at the same time last year.

Meanwhile, South Korea's crude imports from Saudi Arabia rose in May even though the OPEC-led push to curb supply was last month extended until the end of next March. Saudi Arabia is the de facto leader of OPEC.

South Korea imported 4.23 million tonnes of crude oil, or 999,680 bpd, from the world's top crude exporter in May, up 18.6 percent from 3.56 million tonnes in April.

Overall last month, the world's fifth-biggest crude importer shipped in 12.37 million tonnes of oil, or 2.93 million bpd, the data showed, steady with 12.43 million tonnes a year ago.

In the first five months of 2017, South Korea imported 60.62 million tonnes of crude, or 2.94 million bpd, up 1.5 percent from 59.73 million tonnes over the same period in 2016.

Final data for May crude oil imports by state-run Korea National Oil Corp (KNOC) is due later this month. (Reporting by Jane Chung; Editing by Joseph Radford and Tom Hogue)