Shares of the following companies had unusual moves in South Korea trading. Stock symbols are in parentheses and prices are as of 9:59 a.m. in Seoul.

The Kospi index fell 0.7 percent to 1,931.31. The gauge has fallen 2.9 percent this week, poised for its steepest drop since November.

Celltrion Inc. (068270) (068270 KS), a biopharmaceutical company, rallied 13 percent to 42,750 won. The company plans to issue 57.8 million bonus shares to shareholders, according to a regulatory filing.

The company, which also announced a share buyback plan this week, may be trying to boost shareholder value, Shinyoung Securities Co. said in a report today. Earnings will start to improve in the second half, the brokerage said.

Dongkuk Steel Mill Co. (001230) (001230 KS), South Korea’s third- largest steelmaker, added 2.4 percent to 17,150 won. The company plans to halt operations at a steel plate factory in Pohang, South Korea, according to a regulatory filing.

The company will be able to lower fixed costs with little production disruption on increased productivity at other plants, Hana Daetoo Securities Co. said in a report today.

Halla Engineering & Construction Corp. (014790) (014790 KS) retreated 2.1 percent to 11,450 won. The builder’s first-quarter operating profit dropped 27 percent to 13.4 billion won ($12 million), according to a regulatory filing.

SK C&C Co. (034730) (034730 KS) advanced 3.6 percent to 95,800 won. The company’s earnings momentum will strengthen in the second half, Woori Investment & Securities Co. said in a report today.

To contact the reporter on this story: Saeromi Shin in Seoul at sshin15@bloomberg.net

To contact the editors responsible for this story: Darren Boey at dboey@bloomberg.net;