It was an extremely turbulent day for U.S. stocks driven by deep fears about China’s economic slowdown.

Stocks tanked at Monday’s start, with the Dow plunging more than 1,000 points, following the lead set by overseas markets as an intensifying rout persisted in all but assets viewed as safe havens.

The Dow was 783 points, or 4.8 percent, lower as of 9:40 a.m. Eastern time. “Mutual funds had very low cash positions going into this, so when investors get scared, they sell their mutual funds, and equity funds have to sell stocks to meet those redemptions”, said Hugh Johnson, chairman of Hugh Johnson Advisors.

China’s dimming outlook is drawing calls for more economic stimulus from Beijing, though earlier government efforts to stop the sell-off in stocks appear to have done little to stabilize markets. The Dow closed Friday’s session in a correction, or off 10 percent from its May high.

In keeping with point No. 1 here, China spooked a fragile market that might, at less lofty valuations, have been able to withstand a growth shock to the world’s second-largest economy.

Underlying the gloom in China is the growing conviction that policymakers and regulators may lack the means to staunch the losses in that nation.

But that story has been completely derailed by China’s economic slowdown.

“What I think we’re seeing is a typical late-stage bull market in which there are precious few shock absorbers for the market to withstand even a modest negative impact”, said Scott Clemons, chief investment strategist at Brown Brothers Harriman. Not only has an apparent bubble in Chinese equities popped, but the country’s economy may be slowing much faster than feared.

“My biggest concern is that global growth momentum is very fragile”. Currencies fell hard in developing economies – particularly those that rely heavily on the export of commodities and oil, both of which China is a big consumer. Still, the conditions that tend to precede a bear market- 20 percent or greater decline-such as a recession, spikes in oil prices, tight monetary policy, and investor euphoria are largely absent. The Russian ruble dropped 2.3 percent to a seven-year low.

Crude oil plunged below $39 a barrel on Monday for the first time since 2009.