UPDATE 1-S.Korea commercial crude inventory down 36.8 pct y/y

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SEOUL, June 20 (Reuters) - South Korea's commercial crude inventory fell nearly 37 percent by end-May from a year ago as high oil prices continued to discourage refiners from making new purchases, state-run Korea National Oil Corp (KNOC) said Friday.

South Korea's four refiners -- SK Energy (096770.KS), GS Caltex, S-Oil Corp (010950.KS) and Hyundai Oilbank Corp -- had 14.51 million barrels of crude left in stocks by May 31, compared to 22.95 million barrels a year before, KNOC's monthly data showed.

Along with the fall, overall private oil stocks by end-May fell 8.9 percent from a year ago to 70.18 million barrels.

"The problem is continuing. High crude oil prices are pressuring refiners to use stocks rather than make new imports," said Uhm Kwang-yong, domestic products analyst at KNOC.

The end-May crude inventory volume was enough to meet 6.7 days of the country's demand, down from 10.9 days on average in the previous year.

"Despite the fall, there won't be a shortage as KNOC has its regular inventory at full," Uhm said.

SK Energy, the country's top refiner, had 10.14 million barrels of crude stocks, down from 15.39 million barrels a year ago.

GS Caltex's May crude inventory nearly halved to 2.15 million barrels from a year ago.