South Korea's KOSPI jumped more than 4 percent in intraday trade on combined buying by foreign investors and institutions, triggering a buy-side sidecar for the first time in two months. Samsung Electronics and SK Hynix each rose more than 7 percent, leading the index rebound.

As of 11:10 a.m. on Oct. 21, the KOSPI was up 237.84 points, or 4.28 percent, at 5,790.58. The index opened up 113.60 points, or 2.05 percent, at 5,666.34 and extended gains. It was up as much as 4.50 percent at one point, recovering the 5,800 level.

On the sharp rise, the Korea Exchange triggered a buy-side sidecar on the main board at 10:51 a.m. That halted the validity of program buy orders for 5 minutes.

The KOSPI buy-side sidecar was triggered for the first time since Aug. 20, about two months ago. This month, sell-side sidecars were triggered twice, on Oct. 13 and Oct. 15.

In flows, foreign investors and institutions are leading the rise. Foreign investors are net buyers of 320.0 billion won on the main board, while institutions are net buyers of 180.0 billion won. Retail investors, by contrast, are net sellers of 980.0 billion won.

Strength in large semiconductor stocks stood out. Samsung Electronics and SK Hynix each surged more than 7 percent, leading the index higher.

Concerns about the profitability of artificial intelligence (AI) investment, which had weighed on the market through the previous day, also appear to be easing somewhat. U.S. AI server maker Super Micro Computer offered preliminary July-September revenue at a level above market expectations, affecting the recovery in investor sentiment ahead of earnings releases from U.S. big tech companies.

Super Micro Computer put preliminary July-September revenue at about 24.8 trillion won to 26.2 trillion won, more than 3.5 times higher than a year earlier. That topped both its previous guidance and the market forecast of about 20.4 trillion won. After the announcement, Nasdaq 100 futures rose about 1 percent.

The Kosdaq was also rising. At the same time, the Kosdaq was up 15.73 points, or 2.01 percent, at 797.70.