HONG KONG, Sept. 7 (Xinhua) -- Hong Kong stocks dropped below the key 24,000 point level as institutional investors switched their portfolio ahead of benchmark Hang Seng Index compiler's adjustment of its indices and weightings calculations.

The Hang Seng Index fell 67.79 points or 0.28 percent to close at 23,982.61 as China Mobile, the market's largest stock measured by capitalization, was under selling pressure as their weighting on the benchmark Hang Seng Index will be cut beginning next week.

Index compiler HSI Services will adjust its indices and weightings Monday when HSBC's weighting will narrow from 18.23 percent to 15 percent and that of China Mobile will be sliced from 17.19 percent to 12.25 percent.

The Hang Seng Index opened at 24,036.36 and once dropped 168.68 points to the day's lowest 23, 881.72 during the afternoon session. But bargain investors' move pushed the index to pare its losses towards closing.

Turnover rose to 109.06 billion HK dollars (14.02 billion U.S. dollars) from Thursday's 79.41 billion HK dollars (10.2 billion U.S. dollars).

China Mobile, the country's largest mobile phone operator, plunged 2.42 percent to 101 HK dollars, pulling down the index by 110.67 points.

HSBC, the market's second largest stock measured by capitalization, gained 0.07 percent to 139.2 HK dollars.

Property sectors were weaker ahead of the HSI's adjustments. Hutchison, one of Hong Kong's largest house developer controlled by Li Ka-shing, slumped 2.19 percent to 75.9 HK dollars. SHK Properties fell 1.48 percent to 106.4 HK dollars. Hang Lung lost 3.75 percent to 29.55 HK dollars. Henderson Land weakened 3.23 percent to 54 HK dollars.

Hong Kong Exchange continued to rocket 6.76 percent to 158 HK dollars, 31.67 percent higher than its prince a month ago.

Most banks of China's mainland rose though China's central bank announced to raise the reserve requirement for the country's commercial banks by 0.5 percentage points to 12.5 percent as of Sept. 25.

The move was the seventh of its kind by the central bank this year to curb liquidity and the excessive growth in lending.

ICBC, China's biggest lender, gained 0.98 percent to 5.14 HK dollars. Bank of China, the country's second largest lender, added 0.51 percent to 3.94 HK dollars. China Construction Bank, the third largest bank in China, 1.46 percent to 6.94 HK dollars. Ping An surged 1.88 percent to 81.4 HK dollars.

Bank of Communications, which will be added to the HSI as its 40th constituent Monday, rose 1.67 percent to 9.14 HK dollars.

China Life, the country's largest life insurer, dipped 0.27 percent to 37.25 HK dollars.

Oil sectors were stronger with higher oil prices on the global market. Petro China, the country's largest oil producer, advanced 1.08 percent to 11.28 HK dollars. Sinopec, Asia's largest oil refiner, added 1.06 percent to 8.56 HK dollars. CNOOC, China's largest offshore oil producer, soared 2.73 percent to 9.78 HK dollars.

China Cosco, the country's largest shipping conglomerate, once hit an all-time high at 23 HK dollars before jumping 5.76 percent to 22.95 HK dollars.