The index opened in the red with an 18-point loss in the morning and plunged further just before the at-the-closing session, closing 29.75 points lower, despite a slight recovery early afternoon.
Trading value on the Ho Chi Minh Stock Exchange (HoSE), on which the index is based, increased by nearly 20 percent to VND25.92 trillion ($1.14 billion), the highest since Jan. 17.
Banking sector stocks led the fall with 18 out of 20 tickers in the red, dragging the market down by 5.02 percent, or 35.5 points.
Top lenders, including state-owned Vietcombank, BIDV and VietinBank, and the private players Techcombank and Sacombank, closed between 4.1-6.94 percent lower.
Most energy stocks closed in the green, led by PET of Petrovietnam General Services Corporation and PGC of Petrolimex Gas Corporation, both up 6.9 percent. GAS of state-owned PetroVietnam Gas gained 4.5 percent to its highest value in nearly three months.
PLX of fuel distributor Petrolimex, PVT of PetroVietnam Transportation Corporation and PVS of PetroVietnam Technical Services Corporation, rose by between 1.35 and 2.8 percent as Brent crude oil prices rose 1.63 percent to $96 per barrel in the morning session.
Other blue-chip gainers included VJC of budget airline Vietjet, up 5.4 percent, and SAB of brewer Sabeco, up 5.2 percent.
The VN30-Index, representing the 30 largest capped stocks, fell 40.85 points, with 26 tickers in the red. Overall, 322 tickers on the HoSE fell, against 132 gainers.
Foreign investors continued to net sell to the tune of VND295 billion, focusing on HPG of steelmaker Hoa Phat, HDB of HCMC-based lender HDBank, and VIC of biggest private conglomerate Vingroup.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, dropped 1.38 percent while the UPCoM-Index for the Unlisted Public Companies Market lost 1.5 percent.