The Shanghai Composite Index lost 0.1% to close at 2,816.69 and the Shenzhen Composite Index dropped less than 0.1% to end at 1,232.54.
"The market will keep on being unstable. There could be a rally this week, however, it cannot last long as there is not enough power to support it," said Cai Dagui, an analyst in Ping'an Securities, based in Shenzhen.
Elsewhere, benchmarks in Taiwan, Singapore and New Zealand also fell. Markets in Japan were closed Monday for a national holiday.
In currencies, the euro fell to $1.4054 from $1.4136 late Friday. The dollar weakened to 79.02 yen from 79.11 yen.Benchmark oil for August delivery was down 46 cents to $96.78 a barrel in electronic trading on the New York Mercantile Exchange. Crude rose $1.55 to settle at $97.24 on Friday.