Samsung Heavy Industries Co., a South Korean major shipbuilder, said Monday its earnings dropped 20.6 percent in 2013 from a year earlier due to one-off factors, such as special bonuses payments.

Net profit reached 632.2 billion won ($583.7 million) in 2013, compared with 796.4 billion won the previous year, the company said in a regulatory filing.

Sales rose 2.4 percent to 14.83 trillion won during the period, while operating profit nosedived 24.2 percent to 914.2 billion won.

"The poor performance was caused by a decreased operating profit stemming from one-off spendings, such as special bonus payments," the company said.

The company is to pay a yearly dividend of 500 won per ordinary share and 550 won per preferred share, totaling 108.49 billion won.

Shares of Samsung Heavy fell 2.7 percent to 34,250 won on Monday on the Korea Exchange. (Yonhap News)