The benchmark Chinese stock index dropped more than 4 percent Friday as investors took profits from blue chip shares on concerns they are over-priced following strong rises over the past months.

The key Shanghai Composite Index fell 4.03 percent to 2,673.21points. The benchmark index on the Shenzhen Stock Exchange dropped4.58 percent to close at 7,348.03 points.

China Life Insurance was down 7.2 percent to 35.99 yuan; Baoshan Iron and Steel declined 6.48 percent to 8.81 yuan and China Unicom fell 4.12 percent to 4.65 yuan.

Analysts also say investors are concerned that regulators may soon take protective measures to prevent a stock market bubble from bursting.

The Shanghai index dropped more than 7 percent this week. During the first three weeks of the new year, it had risen nearly 10 percent. The benchmark index gained more than 130 percent last year.

Wang Xingjun, an analyst with the Donghai Securities, said the declines this week are normal following a long bullish period and investors should not be too pessimistic.