The KOSPI ended on April 21 at 6,388.47, surpassing the previous record close of 6,307.27 set on Feb. 26 after 2 months. It also rose above the previous intraday record of 6,347.41. Market capitalisation hit a record 5,236.2 trillion won.

The Korea Exchange said the KOSPI plunged in March due to the impact of the U.S.-Iran war but rebounded in April and extended gains on expectations for semiconductor results and improving foreign investor flows. It said investor sentiment recovered as expectations for an improvement in the semiconductor industry grew, based on expanding global AI memory demand.

The Korea Exchange said foreign investors, who had been net sellers from February to March, shifted to net buying in April. Foreign investors were estimated to have net bought 5.6 trillion won of electrical and electronics shares, 1.1 trillion won of chemicals and 0.5 trillion won of machinery and equipment in the KOSPI market from April 1 to 21.

In the KOSPI market on the day, foreigners and institutions led the index higher with net purchases of 1.3342 trillion won and 737.7 billion won, respectively.

Performance by country also stood out. The KOSPI's rise in April was 26.4 percent, ranking first among G20 countries, and the cumulative gain from January to April was also the highest at 51.6 percent.

Japan rose 15.2 percent, Turkey gained 13.2 percent and the U.S. S&P 500 climbed 8.9 percent, posting smaller increases than South Korea.

Still, demand for profit-taking after a sharp short-term rise and uncertainty in the Middle East were cited as variables.

A Korea Exchange official said the continued pursuit of the government's capital market advancement policy, the development of the AI industry and improving semiconductor results were positive factors. The official said the possibility of widening geopolitical risks should be watched.