Rising sales of imported cars in Korea pose a threat to the nation’s largest automaker Hyundai-Kia Automotive Group, according to global credit rating agency Moody's Investors Service.

Sales of imported cars here soared in the year's first half. If the trend continues, market leader Hyundai-Kia could face a serious challenge, Moody's said in a weekly report released on Monday.

Foreign car sales here hit an all-time high last month of 7,629 units, up 44.5 percent on-year. The share of imports in the overall market climbed from 4.5 percent to 5.6 percent.

Moody's predicts that the market share of imports in Korea will top 10 percent within two or three years, as global automakers are trying to lure Korean drivers by introducing lower-priced models and extending their after-sales service systems and marketing networks.

Hyundai-Kia took up 73 percent of the domestic market in the first six months of this year.