World markets fell overnight, pulled down by poor economic news and the surprise announcement that the International Energy Agency would release oil from strategic reserves.

Federal chairman Ben Bernanke has provided investors with little incentive to commit fresh funds to Wall Street as the central bank cut its US economic growth forecast for 2011.

Stocks fell in Europe and the US and the euro weakened amid concern Europe's debt-crisis is worsening and America's economic recovery is running out of puff.

A soaring debut by LinkedIn contrasted with a drop in semiconductor stocks including Intel as data on US home sales and manufacturing fell short of expectations.

Silicon Valley is where the young and thin dream of making millions on the next hot tech startup. Reid Hoffman is portly, "old" and far more successful than most can ever hope to be.

NASDAQ's dream of buying its bigger, older and more famous rival, the New York Stock Exchange, has been shattered

Disappointing US economic data prompted a selloff in oil overnight, which dropped more than 8 per cent. Stocks on Wall Street fell, with losses accelerating towards the close.

Declines in commodities such as gold, silver and oil dragged stocks lower on world markets overnight.

Nasdaq has appealed to shareholders in NYSE Euronext, pressing the case for its $US11.3b takeover offer, after the NYSE board summarily rejected the bid and said it would stick to a lower-priced deal to merge with Germany's Deutsche Brse.