The KOSPI slid more than 3 percent early on Sept. 14, falling below the 6,700 level. The index, which moved around 7,000 last week, is extending losses as U.S. rate uncertainty and geopolitical burdens persist, with foreigners and institutions selling in tandem.

As of 9:22 a.m., the KOSPI is down 217.54 points, or 3.15 percent, from the previous session at 6,692.37. It opened down 217.30 points, or 3.14 percent, at 6,692.61.

On Sept. 11, the KOSPI closed down 124.01 points, or 1.76 percent, at 6,909.91. It had earlier regained the 7,000 level on a closing basis, but then slipped back to the 6,900 level, and early on Sept. 14 it also gave up 6,700.

In the main board market, foreigners are net sellers of 980.2 billion won. Institutions are also dumping shares, selling 272.3 billion won. Individuals are net buyers of 1.14 trillion won, absorbing the selling.

Semiconductor stocks are leading the index lower. Samsung Electronics is trading at 250,750 won, down 3.37 percent from the previous session, while SK Hynix is down 5.35 percent at 1,715,000 won.

Other large-cap stocks are mostly weaker, including SK Square, down 7.16 percent, Samsung Electro-Mechanics, down 5.00 percent, LG Energy Solution, down 2.22 percent, Hyundai Motor, down 4.18 percent, Samsung Biologics, down 1.06 percent, and Samsung Life Insurance, down 3.41 percent. KB Financial is up 0.73 percent.

The KOSDAQ is also falling. At the same time, the KOSDAQ is down 15.26 points, or 1.86 percent, from the previous session at 805.38.

In the Seoul foreign exchange market, the won-dollar exchange rate is at 1,345.60, up 1.80 won, or 0.13 percent, from the previous session.

Recently, the KOSPI has been seeing volatility expand sharply around the 7,000 level depending on foreign flows and moves in semiconductor stocks. Even after regaining 7,000 last week, repeated large-scale foreign selling has made it difficult for the index to settle.

Han Ji-young (한지영), an analyst at Kiwoom Securities, said support near the KOSPI's 7,000 level and whether foreigners resume net buying are becoming important in the domestic stock market. Han said macro uncertainty late in the week prompted net foreign selling, sending the index back down to the 6,900 range.

Han added that foreigners will be the flow driver that can determine the market's direction going forward. Han said whether foreigners resume net buying while digesting the September U.S. Federal Open Market Committee event will be a condition for the index to settle at 7,000.