Korea's financial authorities said Wednesday they are considering imposing a cap on the proportion of single-stock leveraged exchange-traded funds (ETFs) in individual investment portfolios as part of efforts to curb extreme stock market volatility.

Finance Minister Koo Yun-cheol and the heads of other financial authorities discussed the measure during an emergency meeting in Seoul. One option under consideration is to cap such ETFs at 20 percent of retail investors' portfolios, although no decision has been made on the threshold.

"The participants shared the view that single-stock leveraged ETFs have contributed to stock market volatility, and vowed to come up with swift and bold countermeasures," the finance ministry said.

The discussion comes as regulators weigh how much concentrated, leveraged exposure retail investors should be allowed to take on in a market that can move sharply when trading is heavily focused on a small number of names. Any limit would add another layer of oversight to a product that can amplify both gains and losses, making the pending decision relevant for brokerages, ETF issuers and investors who use these funds as short-term trading tools.

Finance Minister Koo Yun-cheol, center, poses with other financial authorities before the emergency meeting in Seoul on Wednesday. From left are senior presidential secretary for economic growth Ha Jun-kyung, Financial Services Commission Chairman Lee Eog-weon, Koo, Bank of Korea Gov. Shin Hyun-song and Financial Supervisory Service Gov. Lee Chan-jin. Yonhap