Seoul shares tumbled around six percent Wednesday morning, dropping below the four-thousand mark, following an overnight slump in U.S. tech stocks.

The benchmark Korea Composite Stock Price Index(KOSPI) opened down one-point-61 percent at four-thousand-55-point-47 and continued to extend its losses.

By 10:34 a.m., the KOSPI was trading at three-thousand-870-point-96, down more than 250 points, or six-point-eight percent, from the previous session's close.

The index marked three-thousand-996-point-25, down three-point-04 percent from Tuesday's close, as of 1:35 p.m.

The sharp decline comes just seven trading days after the main bourse surpassed the four-thousand mark for the first time.

Amid the sharp drop, the Korea Exchange said a sidecar was activated at 9:46 a.m., and lasted five minutes, after the KOSPI 200 Futures Index fell five-point-two percent, or 30-point-35 points, from the previous trading day to 552-point-80.

On the secondary market, a five-minute halt was activated at 10:26 a.m. after the tech-heavy KOSDAQ 150 Futures Index dipped six-point-23 percent from the previous day.