Chinese stocks continued their three-week slide Tuesday, while most of the rest of Asia's markets bounced back ahead of a key meeting on Greece's debt crisis.
The Shanghai Composite Index dropped 3.2 percent by midday, reversing gains from a day earlier, while the Shenzhen Composite Index dropped 5.6 percent.
The losses raise fresh questions about Beijing's ability to contain the stock market plunge, which has already wiped out an estimated $3 trillion in market value.
The government recently announced a series of moves to reassure investors, including pouring billions of dollars into the market and halting initial public offerings.
Elsewhere in Asia, markets mostly recovered Tuesday, with Tokyo, Sydney Hong Kong, Tapei, and Wellington all seeing gains.
Investors are keeping a close watch on Tuesday's emergency meeting of eurozone leaders, where debt-stricken Greece is expected to offer a new proposal aimed at securing an international bailout deal.
Failure to reach a deal soon could mean that Greece defaults on more of its debt, leaves the European Union and discontinues use of the euro currency.