(CNN) -- Asian stock markets are recording sharp declines Friday, extending a global equity sell-off after Wall Street had its worst day since the 2008 financial crisis.

Australia's All Ordinaries dropped 4.3%, Japan's Nikkei shed 3.5% and South Korea's Kospi lost 3.6%.

The Dow tumbled 512 points Thursday -- its ninth deepest point drop ever -- as fear about the global economy spooked investors.

"The conventional wisdom on Wall Street was that the economy was growing -- that the worst was behind us," said Peter Schiff, president of Euro Pacific Capital. "Now what people are realizing is the stimulus didn't work, and we may be headed back to recession."

U.S. markets were already sharply lower on widespread worries, including the weak job market. But the selling gained momentum as Japanese and European policymakers stepped in with dramatic measures to shore up their financial markets.

There's "total fear" in the market, said Bob Doll, chief equity strategist at the world's largest money manager, BlackRock.

All three major indexes tumbled more than 4% Thursday and erased all their gains for the year. The indexes have also pushed into "correction" territory -- defined as a 10% drop from recent highs. The Dow, Nasdaq and S&P 500 have all fallen 10% in just the last 10 days.

"In the last two weeks, we've been through the ringer," said Rich Ilczyszyn, market strategist with futures broker Lind-Waldock. "When we start looking at the recovery, there's nothing to hang our hats on anymore."

The market's fear gauge -- the VIX -- surged 35.8% to a reading of 31.8. A level above 30 signals a high degree of fear.

At the closing bell, the Dow Jones industrial average was down 512 points, or 4.3%, with Alcoa, Caterpillar and Bank of America among the biggest drags on the blue chip index. Thursday's sell-off marked the steepest point loss since October 2008.

The S&P 500 was down a staggering 60 points, or 4.8%.

The Nasdaq lost 136 points, or 5.1%. Some of the better performing tech stocks, Apple, Google and Netflix were all down between 2% and 3%.

Fears about a global slowdown are at the forefront of investors' minds amid recent weak economic data. Early Thursday, the latest reading on jobless claims showed a large number of Americans remain unemployed.

Adding further to investors' jitters, Wall Street is waiting for Friday's jobs report, which BlackRock's Doll said was adding to the selling pressure.

The report is now a bit of wild card after it has come in far below forecasts for the last two months.

Economists surveyed by CNNMoney are expecting the report to show that the U.S. economy created 75,000 jobs in July, marking a slight improvement over the paltry 18,000 jobs added in June.

The unemployment rate is expected to hold steady at 9.2%.

Economic woes weren't contained to the United States. In moves that they hoped would tame financial markets, Japan's government stepped in to weaken the yen, and the European Central Bank decided to re-enter the European bond market for the first time since March.

Those decisions come just a day after Switzerland intervened to curb the Swiss franc's rise.

"It's true that we are in a period of a high level of uncertainty, not only in the euro area but at the global level," ECB President Jean-Claude Trichet said in a press conference Thursday.

The ECB wasted no time and immediately started buying European bonds while Trichet's press conference was still going on. But bond traders were quickly disappointed, after they discovered the central bank only bought Portuguese and Irish debt -- not the Spanish and Italian bonds at the center of the crisis.

The ECB also left interest rates unchanged at 1.5% and initiated a 6-month refinancing operation to add liquidity to European markets.

European stocks plunged. Britain's FTSE 100 tumbled 3.4%, Germany's DAX lost 3.9% and France's CAC 40 fell 3.4%.

In commodities, oil prices slumped 5.3% to $86.63 a barrel.