Shanghai shares closed down more than five percent on Wednesday, a day after their biggest gains in more than six years following a fortnight of heavy losses.

The benchmark Shanghai Composite Index slumped 5.23 percent, or 223.52 points, to 4,053.70 on turnover of 838.1 billion yuan ($137.1 billion). The Shenzhen Composite Index, which tracks stocks on China's second exchange, plummeted 4.79 percent, or 118.10 points, to 2,346.13 on turnover of 691.2 billion yuan.