SK Innovation Co., South Korea's top oil refiner, on Friday said its second quarter profit rose 6.5 percent from a year earlier, aided by better-than-expected results from its petrochemical business.

Net profit reached 626 billion won ($551 million) on a consolidated basis in the April-June period, compared with a profit of 588 billion won a year earlier, the company said in a regulatory filing.

Operating income surged 12 percent on-year to reach 1.12 trillion won over the cited period, while sales dropped 21 percent on-year to reach 10.28 trillion won.

The strong performance was boosted by its petrochemical business amid lower oil prices.

Its refining business logged an operating income of 705 billion won on sales of 7.44 trillion won during the second quarter, while its chemicals unit logged a record operating income of 303 billion won.

Its lubricant business racked up a record operating income of 133 billion won in the second quarter.

In 2014, SK Innovation swung to a loss, falling into the red for the first time in 37 years. Its earnings were hit hard in the fourth quarter as a sharp fall in oil prices hurt the value of its crude stockpiles and cracking margins.

But SK Innovation swung to a net profit in 2015 from a year earlier on improved cracking margins and reduced inventory losses. (Yonhap)