Kia Motors reported a 51 percent slump in operating profit after gains by South Korea's currency, the won, eroded the value of exports and said it expects a "difficult year," sending the stock to the lowest in more than two years.

Fourth-quarter operating income tumbled to 404.2 billion won ($377 million) from 826.9 billion a year earlier, the Seoul- based company said in a regulatory filing Friday. Net income fell 6.7 percent to 737.5 billion won.

Kia's shares fell as much as 5.2 percent after Chief Financial Officer Park Han Woo said 2013 will be a "difficult year" as the won posted the biggest gain last quarter among Asian currencies against the dollar.

- Bloomberg News