Hyundai Motor fell the most in more than three months in Seoul trading as the won rose to an 18-month high, reducing the company’s earnings from exports.

Hyundai dropped 6.7% to close at KRW118,000 (US$106), affiliate company Kia Motors was down 7.2%, the most since July last year, to KRW25,050 (US$22.5) on the biggest trading volume since 5 January, according to Bloomberg data.

The won reached its highest level against the dollar in more than 18 months as South Korea’s central bank raised its economic growth forecast and a European Union rescue package for Greece boosted demand for higher-yielding assets.

The won rose 0.4% to 1,114.13 per dollar after reaching 1,111.38, the highest since 16 September, 2008.

A stronger won cuts into Hyundai’s and Kia’s earnings from exports. Sales outside Hyundai’s home market accounted for half of its revenue last year.

Hyundai and Kia sold a record 4.63m vehicles globally last year aided by a weaker won which allowed them to spend more on promotions.

Separately, Reuters reported Hyundai plans to sell five-year dollar bonds at an indicated price of around 210 basis points over US treasuries.

Sources told the news agency the borrower nominated Barclays Capital, BofA Merrill Lynch, Citigroup, Goldman Sachs and Nomura to handle the sale of the benchmark-sized offering.

"The proceeds will be mostly used to refinance existing debt at Hyundai Motor Manufacturing Czech," said a statement from Standard & Poor's, which has rated the bonds BBB-minus.