Vietnam's benchmark index put an end to its nine-week rally last week by losing total 2.1 percent.
The HNX Index on the Hanoi Stock Exchange lost 1.78 percent to end at 111.78 points. It declined by 0.63 percent on December 8 and edged down 1.4 percent in total last week.
The stock market was dominated by declining stocks, which outnumbered gaining shares by 334 to 136 while 98 others ended flat.
More than 274.4 million shares were traded on both local exchanges, worth 5.66 trillion VND (251.5 million USD).
The trading figures were down about 1.1 percent in both trading value and volume compared to last week’s daily average numbers.
Foreign investors closed on December 11 as net buyers, posting a total net buy value of 11.7 billion VND, which was a reverse from December 8's net sell value of 528.7 billion VND.
The downfall of large-cap stocks, especially financial shares, was to blame for the market volatility on December 11.
The VN30 Index that tracks the movement of the 30 largest stocks by market capitalisation ended down 2.36 percent to 908.29 points, with 25 of the 30 stocks in the basket declining.
Falling stocks included FLC Faros Construction (ROS), steel producer Hoa Sen Group (HSG) and brewer Sabeco (SAB).
On a sector basis, banking, securities and insurance industry indices performed the worst, dropping between 3.9 and 4.8 percent, data on business-finance news site vietstock.vn showed.
The worst decliners among financial shares were Vietinbank (CTG), Sai Gon-Hanoi Bank (SHB), Vietcombank (VCB), Sacombank (STB), Sai Gon-Hanoi Securities (SHS), Saigon Securities Inc (SSI) and insurer Bao Viet Holdings (BVH).
The large-caps and financial stocks mentioned above saw their values plunge at least 5 percent. CTG suffered the most, hitting its daily decreasing limit of 7 percent.
According to tinnhanhchungkhoan.vn, investors started the first trading day of the week on concerns over the arrest of some of Vietnam Oil and Gas Group’s former senior leaders last week.
Sai Gon-Hanoi Securities (SHS) said in a note that investors were quite cautious with the market status.
“They would prefer taking a stand-by position and observing the market to making risky decisions amid uncertainty before the portfolio restructuring period of ETFs and the year-end period,” the brokerage firm said.
“The benchmark index is forecast to continue falling on December 12 and the supportive range for the index would be between 907 and 913 points,” SHS noted.