This was rumoured

Bloomberg headline, citing Chinese securities regulators on Weibo (which is Chinese twitter).

This is the rule that pauses markets after a 5% decline and closes them after a 7% decline. The market closed after just 14 minutes today.

China is looking increasingly reactionary and the markets don't like to see someone making it up as they go along. Futures bounced on this but the next time there's a 15% one-day decline, they'll be badgering for circuit breakers.

Update: The suspension will go into effect Friday. Officials said the circuit breakers didn't work as expected.