SHANGHAI'S key stock index closed flat in the morning session while sentiment improved after the Japanese central bank announced it would pour 12 trillion yen (US$146 billion) to stabilize markets after the devastating quake.

The Shanghai Composite Index edged down 0.02 percent to 2,933.31 after losing as much as 0.6 percent. Turnover rose to 89.2 billion yuan from last Friday morning's 76.09 billion yuan (US$11.58 billion).

The Shenzhen Component Index was up 0.2 percent to 12,873.63.

Steel makers and cement producers led the gainers on speculation that reconstruction projects in Japan may benefit Chinese construction material exporters.

Baoshan Iron & Steel Co rose 2 percent to 7.22 yuan. Inner Mongolian Baotou Steel Union Co jumped by daily limit of 10 percent to 5.27 yuan after the company announced plans to raise as much as 6 billion yuan through issuing new shares to buy iron mines in southwest China.

Xinjiang Tianshan Cement Co added 2.8 percent to 42.85 yuan. Jiangxi Wannianqing Cement Co rose 1.6 percent to 16.79 yuan.

Nuclear plant builders led the decliners. Sufa Technology Industry Co dropped 5 percent to 36.80 yuan. Shanghai Electric Group Co shed 3 percent to 8.57 yuan.