The index is now at 1,055.45 points, the lowest since early May, with 90% of 560 tickers falling. It has fallen 15% from its peak of 1,245 points established in early September.
Trading on the Ho Chi Minh Stock Exchange, on which the index is based, increased by 111% to 23.243 trillion VND (944 million USD).
Foreign investors were net sellers to the tune of 104 billion VND, mainly selling VHM and SSI of leading brokerage SSI Securities Corporation.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, plunged 5.30% while the UPCoM-Index for the Unlisted Public Companies Market closed 3.25% lower.