GLOBAL MARKETS-Shares plunge on global growth, bank fears; U.S. yields fall

* S&P 500 down 10.5 pct for year

* MSCI world stock index down more than 20 pct from record high

* 10-yr Treasury yields hit 1.53 pct, lowest since Aug 2012

* U.S (Other OTC: UBGXF - news) ., European banking shares tumble

* U.S. oil lowest in over 12 years; gold jumps to highest in a year

* Dollar hits lowest vs yen since October 2014 (Updates to close of U.S. markets)

By Sam Forgione

NEW YORK, Feb 11 (Reuters) - Stock indexes worldwide fell on Thursday on fears over the health of the global economy and banking sector, with MSCI's world stock index dropping to more than 20 percent below its all-time high, while safe-haven 10-year Treasury yields hit their lowest since 2012.

Concern over sluggish global growth and doubts over central banks' ability to support the global economy pushed the U.S. benchmark S&P 500 index down 10.5 percent for the year. The FTSEurofirst 300 index of top European shares sank to its lowest level in 2-1/2 years.

The dollar hit its lowest against the safe-haven yen since October 2014, at 110.985 yen, and was on track for its worst week against the Japanese currency since 2008.

"There are mounting concerns about the ability of central banks to continue to prop up asset prices," said Omer Esiner, chief market analyst at Commonwealth Foreign Exchange in Washington. "That's part of why we're seeing assets across the board come under pressure."

Banks in Europe ended 6.3 percent lower, making them the worst-performing sector and widening their losses for the year to more than 28 percent. Shares (Berlin: DI6.BE - news) of Societe Generale (Swiss: 519928.SW - news) , France's second-biggest bank, closed down 12.6 percent after disappointing results.

Worries also hit shares of U.S. banks, with the S&P financial index ending down about 3 percent. Concerns over profitability in a low-growth, low-interest rate environment have knocked confidence in the banking sector this week, particularly in Europe.

YELLEN

The declines came even as Federal Reserve Chair Janet Yellen sought to reassure investors in congressional testimony that the Fed will remain flexible in its approach. The markets, however, do not expect the Fed to raise rates further this year, compared with Fed forecasts that still point to more tightening.

"Credit has been signaling these concerns, and to some extent other markets, and particularly equity, have caught up with what credit had been telling them, which was: We're really worried about global growth, we're really worried that central banks are running out of ammunition," said David Riley, head of credit strategy at BlueBay Asset Management in London.

Yields on benchmark 10-year U.S. Treasury notes hit 1.53 percent, their lowest level since August 2012, on the worries over global growth and the effectiveness of central bank policy.

MSCI's all-country world equity index, which tracks shares in 45 nations, was last down 4.73 points, or 1.32 percent, at 353.35. The index hit its lowest level in more than 2-1/2 years and was last down more than 20 percent from an all-time high.

The Dow Jones industrial average ended down 254.56 points, or 1.6 percent, at 15,660.18. The S&P 500 lost 22.78 points, or 1.23 percent, at 1,829.08. The Nasdaq Composite dropped down 16.76 points, or 0.39 percent, to 4,266.84.

Europe's broad FTSEurofirst 300 index closed down 3.68 percent at 1,195.76.

U.S. crude fell, hitting a 12-year low of $26.05 a barrel as domestic stocks grew and Goldman Sachs (NYSE: GS - news) called for depressed prices until the second half of the year.

U.S. crude hit a more than 12-year low of $26.05 a barrel before settling down $1.24, or 4.52 percent, at $26.21 a barrel. Brent crude settled down 78 cents, or 2.53 percent, at $30.06 a barrel.

Safe-haven spot gold surged 5.3 percent to $1,260.60, the highest in a year. U.S. gold futures for April (LSE: 0N69.L - news) delivery settled up 4.5 percent at $1,247.80 per ounce. (Additional reporting by Clara Denina, Simon Falush Kit Rees and Alistair Smout in London, Dion Rabouin, Tariro Mzezewa in New York, and Abhiram Nandakumar in Bengaluru; Editing by Bernadette Baum and Dan Grebler)