S-Oil reported an operating loss of 164.3 billion won ($136.84 million) for the second quarter. Inventory-related loss narrowed to 169 billion won from 721 billion won in the previous quarter.

The refiner plans to shut its No.1 crude distillation unit (CDU) in the third quarter and No.2 residue fluid catalytic cracker (RFCC) in June and July for maintenance.

The company also said it operated its 669,000 barrels-per-day CDUs in the southeastern city of Ulsan at 99.8% of capacity on average in the April-June period, up from 93.4% in the first quarter.

Shares of S-Oil were down 0.8% as of 1250 GMT, while the wider market <.KS11> was trading 0.1% lower.

($1 = 1,200.6400 won)

By Heekyong Yang and Joyce Lee