The ratio stood at 45.4 percent at the end of March, marking the first time it has exceeded 45 percent since the BIS began tracking the data in the fourth quarter of 1990. This figure represents a notable increase from 44 percent at the end of 2023.
The BIS estimated the government debt at 1,119.3 trillion won ($823.4 billion), the highest level in both won and dollar terms since records began.
The Bank of Korea also issued a warning about growing government liabilities in a June report.
"The continuous deficit in the consolidated fiscal balance since 2019, coupled with unavoidable government spending increases in response to crises such as COVID-19, has led to persistent deficits," the central bank said.
"For a non-key currency country with high external dependence like Korea, a rapid increase in national debt could lead to capital outflows and instability in financial and foreign exchange markets due to a potential downgrade in the country's credit rating," it added.
Despite the rise in government debt, the debt-to-GDP ratios for households and corporations both declined. The household debt ratio fell to 92 percent from 93.6 percent, while the corporate debt ratio dropped to 112.2 percent from 113 percent in the previous quarter.