GLOBAL MARKETS-World stocks at 21-month low as banks plunge

* MSCI world equity index down 0.9 percent at 342.11

* The index lowest since Oct '06, down 20 pct from Nov peak

* Fannie Mae, Freddie concerns trigger selloff in financials

* Yen up on safe-haven demand, oil rebounds slightly

By Natsuko Waki

LONDON, July 8 (Reuters) - Fresh credit fears swept global financial markets on Tuesday, pushing world stocks to their lowest levels since October 2006 as concerns intensified that the financial sector would have to raise more capital.

Banks tumbled across the board after a Lehman Brothers report said a pending accounting change could force Fannie Mae (FNM.N: Quote, Profile, Research) and Freddie Mac (FRE.N: Quote, Profile, Research) to raise an $46 billion and $29 billion respectively at a difficult time, knocking their shares to near 16-year lows on Monday.

In Britain, shares in troubled mortgage bank Bradford & Bingley (BB.L: Quote, Profile, Research) fell 20 percent to record lows, below the price of its planned rights issue, due to concerns over its future.