Wednesday's stock market tumble doesn't seem to have inhibited the Shanghai index's overall upward movement, but investors may want to watch out for high market volatility, as the major stock index took a roller coaster ride Thursday with a maximum swing of over 140 points.

The benchmark Shanghai Composite Index opened at 4,316.57 points, 16 points higher than Wednesday's close, and then surged rapidly above the 4,400 point level at around 11 am. But it was too early to celebrate the gain, as the index made a dramatic dive within the first hour of the second session, a reminder of Wednesday's sudden plunge.

However, the index didn't in fact copy yesterday's crash but regained lost ground and closed at 4407.73, up 107 points or 2.49 percent. Trading value of the market was 142.6 billion yuan, smaller than yesterday's figure.

Also, the Shenzhen Component Index opened at 14,901 points and closed at a new high of 15,562 points with an increase of 5.18 percent, although it fluttered in between. Turnover on the bullish day reached 80.2 billion yuan.

                                Shanghai Composite Index
                                  Source: www.sina.com.cn

Although most blue chips lost relatively less during Wednesday's dive, some failed to perform well compared with the booming index. Sinopec inched up 0.07 yuan and closed at 14.06 yuan. Yangtze Power, operator of the world"s biggest hydropower project, gained 1.64 percent to 17.36 yuan.

Market watchers said yesterday's dive may be the lagged impact of the reserve ratio hike and other monetary tightening measures. But the plunge in the middle of today's trading, however, may be better considered as a test of investors' firmness. As the upward trend of the market appears unshakable, confidence may be the best investment tip for those betting on the nation's economic future.