China's main stock index slipped 0.45 percent on Friday, unable to sustain a brief foray into positive territory as investors grew concerned the government may take action to cool the economy.

The Shanghai Composite Index ended the session at 4,030.26 points, clinging above the psychologically key 4,000 mark after retreating from an intra-day high of 4,052.097.

With the Shanghai index roaring to record highs in recent weeks, gaining 50 percent since the start of the year, the market value of the Shanghai and Shenzhen bourses rose to 17.43 trillion yuan ($2.27 trillion) as of Thursday, more than China's total personal bank savings of 17.37 trillion, media reported.

Central bank governor Zhou Xiaochuan said on Thursday that China may consider taking further steps to cool the economy by raising interest rates or the amount that banks must put aside as reserves rather than lend out.

"Rumours have been spreading that there will be an interest rate hike soon," said Chen Jinren, analyst at Huatai Securities. "A modest increase would be within expectations."

Chen said such monetary policy moves have little impact on the stock market, however, and authorities were not likely to take extreme measures because it was not possible to know whether there was a bubble in the market.

There are signs that heated investor interest in stocks may be cooling, however, especially after Tuesday's stock market retreat -- the Shanghai index's third-largest single-day point loss this year -- on concerns about government steps to rein in the market.

Only 240,000 new A-share stock accounts were opened on Wednesday, compared with an average of 300,000 per day around the time of the May 1-7 holiday, while the pace of the establishment of new funds has also slowed, with only three funds launched or in the process of being launched so far this month.