The total operating profit of 492 companies among the country's top 500 medium-sized firms that filed earnings as of last week reached 3.42 trillion won ($2.52 billion), with their sales rising 4.2 percent to 59.6 trillion won, according to industry tracker CEO Score.
By sector, companies in the electronics segment saw their operating profits more than double over the period, buoyed by strong semiconductor exports, reports Yonhap news agency.
The operating profits of automobile and auto parts businesses increased 18.9 percent during the same period, with other winners including the petrochemical and construction material industries, which advanced 18.2 percent and 11.6 percent, respectively.
Medical instrument companies also returned to profits in the second quarter, amid a resurgence of COVID-19 infections worldwide, the industry tracker added.
The service sector, which includes entertainment firms, however, saw its combined operating profit dip by 36.9 percent due to the sluggish performance of major labels, including YG Entertainment and JYP Entertainment.
Meanwhile, the combined net profits of the 334 companies out of South Korea's top 500 companies by sales reached 59.4 trillion won ($43.6 billion) for the April-June period, up 107.1 per cent from 28.7 trillion won a year ago, according to CEO Score.
The country's two leading chipmakers, Samsung Electronics and SK hynix led the overall increase for the second quarter on rising demand for AI semiconductors, such as high-bandwidth memory (HBM) from U.S. tech giants like Nvidia.
Samsung Electronics, the world's largest memory chipmaker, posted 10.4 trillion won in operating profit for the three-month period ending June, soaring from 668.5 billion won a year earlier. SK hynix's operating profit amounted to 5.5 trillion won for the second quarter, turning from an operating loss of 2.9 trillion won a year earlier.