LONDON (Reuters) - World stocks nosedived and demand for safe-haven bonds and currencies soared on Monday as fears gripped investors that a deteriorating U.S. economy would drag others down with it.

MSCI's main world stock index, a benchmark gauge of stock markets globally, sank 2.6 percent, falling below its 2007 bottom to lows last seen in December 2006.

Its emerging market equities counterpart lost more than 5 percent. Meanwhile, the spread between emerging market bond yields and U.S. Treasury yields, a key gauge of risk appetite, was just off its widest in two years.

"A mixture of weak global economic data, poor corporate data, increasing fears about the possibility of a recession ... have left investors drowning in a sea of red," said Henk Potts, equity strategist at Barclays Stockbrokers.

The pan-European FTSEurofirst 300 was down 4.2 percent, taking its 2008 year-to-date losses to more than 13 percent.

Japan's benchmark Nikkei average earlier lost 3.86 percent to close at a two-year low and MSCI's main emerging market stocks benchmark was down 3.9 percent.