(Reuters) -- LG Chem bought around 50 KT of open-spec naphtha for first-half July arrival at Yeosu at a discount of USD 3 a tonne to Japan quote on a cost-and-freight (C&F) basis, lowest level seen in South Korea in nearly eight months, traders said on Wednesday. Sentiment was on a downward spiral since May 13 after Asia's top naphtha buyer Formosa shut one of its three crackers following a fire at a pipeline. "Some traders are under pressure to sell their cargoes," said a source. The last time South Korea saw spot naphtha prices in discount was on Oct. 8, 2010.