South Korea's KOSPI fell more than 6 percent on a sharp drop in semiconductor shares, sliding to the 6,000 level for the first time since May 4. The Kosdaq, which opened higher, also turned lower, while the won-dollar exchange rate is rising again.

As of 12:17 p.m. on July 13, the KOSPI is down 509.87 points, or 6.82 percent, from the previous session at 6,966.07.

The index opened 63.91 points, or 0.85 percent, lower than the previous close at 7,412.03 and rose as high as 7,529.07. It then fell sharply as selling poured in, led by semiconductor shares. This is the first time since May 4 that the KOSPI has fallen below 7,000 during the session.

In the main board market, individuals are net buyers of 1.8686 trillion won. Foreigners and institutions are net sellers of 1.4481 trillion won and 472.5 billion won, respectively.

The Korea Exchange triggered a sell-sidecar on the main board at 10:34 a.m. Program sell orders were suspended for 5 minutes after KOSPI 200 futures stayed down more than 5 percent from the reference price for at least 1 minute.

Losses were led by semiconductor-related shares among the top stocks by market capitalisation. Samsung Electronics is trading at 263,000 won, down 22,000 won, or 7.72 percent, from the previous session.

SK Hynix fell 275,000 won, or 12.61 percent, to 1,905,000 won. It broke below 2,000,000 won during the session and then slid into the 1,900,000 won range. SK Square fell 14.90 percent and Samsung Electro-Mechanics slid 16.98 percent.

By contrast, some large non-semiconductor stocks are rising, including LG Energy Solution, up 1.23 percent, KB Financial Group, up 2.77 percent, and Samsung Biologics, up 0.29 percent.

The Kosdaq also turned lower. At the same time, the Kosdaq is down 25.06 points, or 2.99 percent, from the previous session at 812.37.

The Kosdaq rose more than 2 percent early in the session to top the 850 level, but gave up all gains as the KOSPI plunged and risk-off sentiment spread.

The won-dollar exchange rate is trading at 1,506.80, up 4.80 won, or 0.32 percent, from the previous session. The exchange rate, which fell early, turned higher again as foreign selling and stock market instability grew.

Han Ji-young (한지영), an analyst at Kiwoom Securities, said concerns over a peak-out in the memory market have not been resolved despite a successful SK Hynix ADR listing. Han said a string of recent sharp falls in semiconductor shares is increasing investor fatigue and causing demand to pull back.

Han said higher oil prices and U.S. Treasury yields, amid renewed U.S.-Iran geopolitical tensions, are also weighing on the market.