The index gradually slid throughout the day and closed nearly 30 points lower. It has lost nearly 72 points in the last three sessions.
Asian markets, including the Nikkei 225 and Hang Seng Index, also ended in the red Monday amid reports of the Omicron variant spreading to several countries, including Thailand.
Trading value on the Ho Chi Minh Stock Exchange (HoSE), on which the index is based, fell 4.5 percent to VND31.39 trillion ($1.36 billion).
The VN30 basket, comprising the 30 largest capped stocks, saw 22 tickers in the red, with HDB of HDBank falling 6.1 percent.
The ticker is now at a two-week low after falling for three consecutive sessions.
KDH of real estate firm Khang Dien House plunged 6 percent, also to a two-week low.
GAS of state-owned Petrovietnam Gas continued its downward trend, hitting the lowest since Sep. 27.
HPG of steelmaker Hoa Phat Group fell 4 percent to the lowest in over four months.
Five blue chip tickers bucked the trend, with POW of electricity producer Petrovietnam Power Corporation gaining 2.6 percent.
SSI of leading brokerage SSI Securities Corporation rose 1 percent after two losing sessions.
Foreign investors ended a chain of eight net buying sessions with a net purchase of VND309 billion, focusing on VHM of real estate giant Vinhomes and SSI.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 2.99 percent, while the UPCoM-Index for the Unlisted Public Companies Market dropped 2.6 percent.