SEOUL - South Korea's anti-trust agency said on Wednesday it would impose a combined 669 billion won ($581 million) in fines on six companies for what it said was involvement in a liquefied petroleum gas (LPG) price cartel.

The Fair Trade Commission (FTC) said in a statement that four oil refiners -- SK Energy, GS Caltex, S-Oil and Hyundai Oilbank -- and two LPG companies -- E1 and SK Gas -- were found to have engaged in price fixing activities between 2003 and 2008. ($1=1152.0 Won) (Reporting by Rhee So-eui; Editing by Jon Loades-Carter)