Doosan Heavy Industries Co., Korea's top power equipment maker, said Monday that it swung to the black in the second quarter from a year earlier, aided by increased gains from equity ties with affiliates and tough restructuring moves aimed at reducing costs.

Net profit reached 126 billion won ($111 million) in the April-June period on a consolidated basis, compared with a loss of 25 billion won a year earlier, the company said in a regulatory filing.

Operating income surged 58 percent on-year to reach 262 billion won, while sales fell 3.7 percent to 3.59 trillion won over the cited period.

Doosan Heavy said its affiliates' business performance improved a lot on the back of tough restructuring efforts and helped boost its overall bottom line.

Doosan Heavy closed at 24,950 won on the Seoul bourse, up 3.96 percent from the previous session's close.

The benchmark KOSPI index rose 0.19 percent. The second-quarter earnings were released after the market closed. (Yonhap)