Stocks rose for most of July 20 before sliding into the negative zone by the end of the session, putting the brakes on this week's rally.

"The market sentiment remained strong but some investors decided to take the margin on speculation of technical declines," FPT Securities Co's analysts wrote in their daily report.

The benchmark VN-Index on the HCM Stock Exchange lost 0.91 percent to finish the session at 424.47 points, stopping its three-day rising run.

Both trading volume and value were down about 16 percent from a day earlier, totalling 73 million shares, worth nearly 1.06 trillion VND (50.5 million USD).

Blue chips lost value in the last minutes, with the VN30 Index tracking the top 30 largest shares by market capitalisation and liquidity as sinking more than 1 percent to 497.43. Among its 30 members, six advanced, 21 declined and three closed unchanged.

By the end of the session, only insurer Bao Viet Holdings (BVH) and Tan Tao Investment Industry (ITA) still closed at ceiling prices. ITA was the most active stock on a total trade of 9.7 million shares.

Losers outnumbered gainer by 142-100 overall.

On the Hanoi Stock Exchange, the HNX-Index rose to 73.11 points in the morning before falling back to 72.19, a decrease of more than 1 percent over the previous session’s close.

Trading volume dropped 7.7 percent from a day earlier to nearly 64 million shares, meanwhile value of trades reduced 4.5 percent to just 606.5 billion VND (28.9 million USD).

Blue chips on the Hanoi bourse also fell, with the HNX30 also down 1.17 percent to 138.68 points.

Kim Long Securities (KLS) remained the most active in Hanoi yesterday with 9.2 million shares traded, rising 2.9 percent to 10,500 VND (50 cents USD).

Foreign investors turned to be net sellers on the HCM City's bourse yesterday, unloading shares worth 35.4 billion VND (1.7 million USD), but they still concluded as net buyers on the Hanoi exchange with a net buy value of 15.7 billion VND (748,000 USD).

According to Thomson Reuters, foreign investors poured a net value of 1.1 million USD into Vietnam 's stock market from July 1. However, they also withdrew 61.4 million USD from Vietnam 's market in the second quarter.-VNA