KB Financial Group Inc. on Thursday reported its first-quarter net income plunged nearly 30 percent due to increased costs for the compensation of a mishap in sales of equity-linked securities.Net profit reached 1.06 trillion won (US$773 million) in the January-March period, down from a profit of 1.51 trillion won a year earlier, the company said in a regulatory filing.Operating income for the quarter rose to 2.35 trillion won from 2.14 trillion won a year earlier, and revenue fell 6 percent on-year to 23.35 trillion won.The financial holding company said it set aside some 862 billion won in reserve for the compensation of "various cases of incomplete sales" involving equity-linked securities products tracking Hong Kong's H Index.Its nonoperating loss swelled to 948 billion won in the first quarter from 96.2 billion won over the cited period.Its interest income rose 11.6 percent on-year to 3.15 trillion won in the first quarter, with its noninterest income dipping 18.7 percent to 1.26 trillion won.T he group's net interest margin, the difference between interest received and paid, came to 2.11 percent in the first quarter, up from 2.04 percent a year earlier.KB Kookmin Bank's net profit declined to 389 billion won in the January-March period from 932 billion won in profit a year earlier. Its operating profit increased 12.86 percent on-year to 4.33 trillion won despite an 8.9 percent drop in revenue from 49.4 trillion won in 2022 to 45.03 trillion won last year.Source: Yonhap News Agency