China's stock markets have been suspended to limit volatility after shares plunged 7%.
The Shanghai Composite index fell 6.9% and the tech-focused Shenzhen Composite dropped more than 8%.
Following the huge losses seen during 2015, regulators implemented a new system in December which suspends trading if shares fall by 7% or more.
Investors were disappointed by a new survey signalling more bad new for the Chinese economy. The Markit/Caixin manufacturing purchasing managers' index (PMI) fell to 48.2 in December, marking the 10th consecutive month of contraction. Any figure above 50 indicates growth.
Shares in Asia followed the falls. Hong Kong's Hang Send index fell 2.8% and Japan's Nikkei 225 dropped 3.1%.