The index fluctuated around 1,360 points in the morning as brokerages reported technical issues that prevented investors from placing orders.
But with the issues fixed in the afternoon, VN-Index shot up and closed with a nearly 34-point gain, its biggest increase in a day since Feb. 17.
Trading value on the Ho Chi Minh Stock Exchange (HoSE), on which the index is based, fell 7 percent to VND26.6 trillion ($1.15 billion). The bourse saw 147 tickers gain and 226 lose.
Foreign investors were net buyers to the tune of VND2.08 trillion, the highest in nearly two months. Strongest pressure was seen on VHM of real estate giant Vinhomes, MBB of MBBank and HPG of steelmaker Hoa Phat Group.
The VN30 basket, comprising the 30 largest capped stocks, saw 26 tickers gain, led by MWG of electronics retail chain Mobile World with a ceiling increase of 7 percent.
The gain made up for a 6.9 percent loss Tuesday. It is now 0.4 percent from its previous peak, 40 percent up from the beginning of the year.
PNJ of Phu Nhuan Jewelry rose 6.9 percent to a new peak, having risen 33 percent this year.
Other strong gainers include GAS of state-owned Petrovietnam Gas, up 6.6 percent, MSN of conglomerate Masan Group, up 6.4 percent and TCH of real estate company Hoang Huy Investment Financial Services, up 6.3 percent.
However, three tickers bucked the trend, led by BVH of insurance company Bao Viet Holdings with a 2.5 percent drop, followed by POW of electricity producer Petrovietnam Power Corporation, down 0.4 percent and VPB of private lender VPBank, down 0.4 percent.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, gained 0.41 percent, while the UPCoM-Index for the Unlisted Public Companies Market rose 0.08 percent.