The measure has plunged 11 percent in six days, the most since the U.S. was stripped of its AAA credit rating by S&P in August 2011. In the United States, stocks surged in a “head fake” rally Tuesday, sending the Dow 441 points higher, before gains were wiped out and the market traded sharply lower into the close.

The Dow Jones industrial average rose 334, or 2.1 percent, to 15,996 as of 1:44 p.m. Eastern time.

The Stoxx Europe 600 index was 1.5 percent lower midmorning, following a 4.2 percent gain on Tuesday.

Markets have been volatile for weeks on deepening unease over the ramifications of slowing growth in China, the world’s second-largest economy and the driver of much of global growth over the past decade. Investors interpreted the move as an attempt to bolster a sagging economy.

But traders said the market remained vulnerable to sudden selloffs, as investors who bought shares using margin financing continue to deleverage, and as China’s economic outlook remains weak. However, he also stated that the situation could still change before the Fed’s next policy meeting scheduled for mid-September.

Investors also got some encouraging news from a survey indicating that U.S. consumer confidence rebounded this month.

The CBOE Market Volatility Index was still elevated at 36, indicating significant uncertainty, but the “fear index” as it is known was well below the previous day’s 6-1/2 year peak of 53.3.

Hong Kong’s Hang Seng index fared only slightly better than the mainland, shedding 0.3% to 21,328.55 points. Britain’s FTSE 100 rose 3.8 percent.

The dollar rose to 119.60 yen versus 118.66 yen late Wednesday. Tokyo’s Nikkei 225 was up 2 percent at 18,753 and Seoul’s Kospi gained 1.1 percent to 1,915.70.

The benchmark Shanghai Composite Index jumped 5.34 percent to 3,083.59 on Wednesday, the smaller Shenzhen Component Index up 3.58 percent to 10,254.35 points.

Earlier, European and Asian markets produced mixed results.

Brent crude oil, which is used to price worldwide trading, also gained 29 cents a barrel, to $43.50.

In economic news, the Commerce Department said orders for durable goods, or items expected to last at least three years, rose 2 percent last month after a 4.1 percent gain in June.

Despite improving U.S. employment and housing data, a voting member of the U.S. central bank raised doubts Wednesday on the timing for a rate hike.