South Korea's KOSPI on Tuesday tumbled again after a day, sliding back to the 7,700 level. It had surged more than 8 percent the previous day to regain 8,000, but losses widened as foreign investors and institutions sold together and heavyweight chipmakers weakened. A selling sidecar was also triggered intraday on the main board.

The KOSPI closed down 366.11 points, or 4.52 percent, at 7,730.82. It opened down 197.16 points, or 2.44 percent, at 7,899.77 and narrowed losses to as little as 7,996.68 during the session, but selling intensified in the afternoon and the index sank.

It ended the previous day up 612.52 points, or 8.18 percent, at 8,096.93, regaining 8,000 after a day. But it fell more than 4 percent again on Tuesday, failing to settle above 8,000.

A selling sidecar was triggered during the session. The Korea Exchange said program sell orders were suspended for 5 minutes on the main board at 1:16:25 p.m. due to moves in KOSPI 200 futures.

A buying sidecar was triggered during Monday's sharp rebound in the KOSPI. With program buy orders suspended temporarily a day earlier and program sell orders halted on Tuesday, volatility in local equities appears to have surged sharply over a short period.

Foreign investors and institutions drove the index lower. On the main board, retail investors were net buyers of 483.43 billion won, while foreigners and institutions were net sellers of 317.04 billion won and 183.90 billion won, respectively.

Unlike the previous day, when institutions stepped in with large net buying to lead the rebound, both foreigners and institutions were net sellers on Tuesday.

Most top market-cap stocks fell. Samsung Electronics closed down 19,500 won, or 6.06 percent, at 302,500 won. It had regained the 300,000-won level the previous day and narrowly held onto the milestone.

SK Hynix ended down 167,000 won, or 7.54 percent, at 2,048,000 won. It also held the 2 million-won level, but the drop was steep.

SK Square fell 6.78 percent and Samsung Electro-Mechanics slid 8.38 percent. Hyundai Motor and LG Energy Solution dropped 5.79 percent and 2.77 percent, respectively. Samsung Life fell 6.36 percent and Samsung C&T dropped 5.01 percent.

HD Hyundai Heavy Industries rose 4.74 percent, showing a differentiated move among the top market-cap stocks.

The weakness is seen as the result of profit-taking after Monday's sharp rebound overlapping with foreign selling. Recently, local equities have been swinging sharply day to day, led by heavyweight chip stocks.

Samsung Electronics and SK Hynix lifted the index on Monday by regaining the 300,000-won and 2 million-won levels, respectively, but selling emerged again on Tuesday and led the index lower.

The KOSDAQ also fell. It ended down 16.18 points, or 1.67 percent, at 951.63. It had rebounded more than 6 percent the previous day to regain 960, but turned weaker again on Tuesday.

In the Seoul foreign exchange market, the won was quoted at 1,525.30 per dollar, down 0.80 won from the previous session. As the exchange rate remains at an elevated level in the 1,520-won range, pressure on foreign investor flows is also continuing.

The market sees foreign selling, the direction of heavyweight chip stocks and the exchange rate as key drivers of volatility in local equities for the time being. With the buying sidecar on Monday and the selling sidecar on Tuesday triggered a day apart, wariness about short-term swings is also growing.

Han Ji-young (한지영), a researcher at Kiwoom Securities, said, "This shows that recent index moves have become disorderly to the extent that they cannot keep up with actual stock price volatility," and added, "As long as most of the supply and demand is concentrated in semiconductors and an environment persists in which semiconductors have a high influence on the KOSPI, we will frequently face such disorderly price movements."