ATMs of major local banks line a street in Seoul in April. (Newsis) South Korean lenders are tightening access to unsecured borrowing as concern grows over surging household debt, with internet-only banks joining a pullback that started with major commercial lenders.K Bank went furthest among online lenders, suspending all new overdraft accounts through July 31, the company said Tuesday. It has also capped daily credit loan applications and plans to lower limits for high-income borrowers.Kakao Bank, the country's largest internet-only bank, said it will cut the limit on overdraft accounts to 100 million won ($66,100) starting Monday — less than half the previous ceiling of 240 million won. From July, it will also cut limits by up to 20 percent for large overdraft accounts with low usage.The lender will also keep its daily cap on new unsecured credit loan applications, restricting requests once they exceed its internal threshold. Products for mid- and low-credit borrowers will be exempt.Toss Bank is preparing similar curbs, with plans to lower the maximum on unsecured credit loans to 100 million won and overdraft accounts to 50 million won, one-third of the current ceilings.The moves follow similar steps by Korea's five largest commercial banks, including credit loan caps at KB Kookmin Bank and Hana Bank, online application and refinancing restrictions at Shinhan Bank and Woori Bank, and preferential rate cuts at NH NongHyup Bank.The clampdown accelerated after financial authorities put household debt under emergency monitoring last week and said they would hold weekly checks on lenders that miss loan growth targets. Regulators also urged banks to strengthen voluntary controls, including lower credit loan limits for high-income borrowers and measures to encourage early repayment.The pressure comes after household loans surged across the financial sector, rising by 9.3 trillion won in May, nearly triple the previous month’s increase, as unsecured credit jumped while mortgage growth slowed. Other loans, including personal credit loans and overdraft accounts, swung to a 5.3 trillion won increase from a 2 trillion won decline in April.The trend has carried into June, with credit loans at the five largest commercial banks rising by 1.6 trillion won in the first 10 days of the month, according to local reports. Overdraft balances also climbed by 1.2 trillion won in early June, with roughly half the increase coming over June 5 and 8, when the Kospi tumbled 14 percent, suggesting retail investors used the accounts to buy the dip.Authorities have also linked the surge to stock investment demand, with the Bank of Korea saying in its May financial markets report that other loans "rose sharply as individuals' large-scale stock investments coincided with seasonal funding demand in May."