The U.S. stock market and other risk assets got hammered on Thursday as investors took money off table ahead of Friday's U.S. jobs report and a worsening debt crisis in Europe.

The Dow Jones Industrial Average fell 512.76 points, or 4.13 percent, to close at 11,383.68. The S&P 500 Index fell 60.27 points, or 4.78 percent, to end at 1,200.07.  The NASADQ fell 5.08 percent.

Crude oil prices, an indicator of the market's sentiment on the global economy, plunged 5 percent to settle at $86.63. 

Investors are concerned about the economy and financial system on both sides of the Atlantic.

In Europe, the contagious sovereign debt crisis is threatening Italy, euro zone's third largest economy.  For months, the market's fear is that the debt crisis would hit a large country like Italy or Spain, which many argue are too big to bail out core Europe.

The European Central Bank (ECB) held a (previously scheduled) press conference earlier in the U.S. session.  While ECB President Jean-Claude Trichet stated the ECB's willingness to buy sovereign bonds in the market, the forcefulness of his language and the actual buying of the ECB wasn't enough to calm the European bond markets.

In the U.S., there wasn't a specific trigger for the sell-off.   

The weekly initial jobless claims data edged slightly above the pessimistic consensus projection of economists.  On Wednesday, the ADP monthly private payrolls gains report also slightly exceeded expectations.

However, the overall picture for the U.S. jobs market and economy still looks gloomy and investors took money off the table ahead of tomorrow all-important July jobs report, which they fear would confirm the weakness of the U.S economy at best and spell more bad news at worst. 

In the two previous months, the U.S. economy only added 18,000 and 54,000 jobs, which is far below what the economy needs to keep up with the expanding labor force, let alone lower the unemployment rate and boost the overall economy.