NEW YORK (Reuters) - The dollar tumbled to a 12-1/2 year low against the Japanese yen on Monday and record levels against the euro and the Swiss franc as emergency liquidity-boosting measures by the Federal Reserve over the weekend failed to ease worries about the U.S. financial sector.

BASEL (Reuters) - UBS Chairman Marcel Ospel, braving investor fury over huge subprime losses, said it was "absolutely necessary" for shareholders to back a 13 billion Swiss franc ($11.94 billion) capital injection from Singapore and an unidentified Middle East investor.