GLOBAL MARKETS-Stocks hit by growth worry; oil rises after OPEC

* Fed chief plays down chances of further stimulus

* World stocks fall after Bernanke comments

* Oil prices advance after OPEC fails to lift output (Adds details, updates prices)

By Wanfeng Zhou

NEW YORK, June 8 (Reuters) - U.S. and European stocks fell for a sixth day on Wednesday on worries about a bleak global economic outlook, while oil prices jumped after OPEC failed to reach an agreement to increase output.

The U.S. dollar hit a one-month low below 80 yen as risk aversion rose, but it rallied against the euro after weaker-than-expected German economic data and on uncertainty over a second Greek bailout package.

Federal Reserve Chairman Ben Bernanke on Tuesday acknowledged that the U.S. economy had slowed but offered no hint that the central bank is considering further stimulus to support growth.

Bernanke's comments, combined with recent weak U.S. labor and manufacturing data, stoked fears that a slowdown in the world's largest economy could dent global growth. For more, see [ID:nW1E7GV010]

"The question marks regarding the growth dynamics for the global economy are becoming bigger and this is weighing on the markets," said Tammo Greetfeld, equity strategist at UniCredit.

World stocks as measured by the MSCI world equity index <.MIWD00000PUS> slipped 0.6 percent. The Thomson Reuters global stock index <.TRXFLDGLPU> lost 0.7 percent. Emerging market stocks <.MSCIEF> also fell 0.7 percent.

The FTSEurofirst 300 <.FTEU3> index of top European shares closed down 0.9 percent at 1,094.30 for the sixth consecutive day of losses. It marked the lowest close in nearly three months.

U.S. stocks were mixed in choppy trading, with gains in energy shares failing to offset bearish sentiment stemming from Bernanke's comments.

Shortly after noon EDT (1600 GMT), the Dow Jones industrial average <.DJI> was up 20.89 points, or 0.17 percent, at 12,091.70. The Standard & Poor's 500 Index <.SPX> was up 0.98 points, or 0.08 percent, at 1,285.92. The Nasdaq Composite Index <.IXIC> was down 10.37 points, or 0.38 percent, at 2,691.19.

Brent crude oil was last up $1.13 at $117.88 a barrel. U.S. crude rose $1.82 to $100.89.

OPEC talks broke down without an agreement to raise output after Saudi Arabia failed to convince other members to lift production. The news raised fears of supply shortages later this year and a price rally that could further limit any global economic recovery. [ID:nL3E7H80BY]

Secretary General Abdullah El-Badri said OPEC hoped to meet again in three months to assess the situation.

"I do not think it is a surprise, but it is a supportive factor and I think this will get us back up to $100 (oil) and pivot around there until something else happens," said Chris Dillman, an analyst at Tradition Energy in Stamford, Connecticut.

DATA, GREECE HIT EURO

The dollar was last down 0.3 percent at 79.87 yen after hitting as low as 79.67 yen, according to Reuters data. Traders said losses picked up speed after a series of automatic sell orders was triggered on the greenback's drop below 80 yen. More "stop-loss" barriers were said to be below 79.50.

The euro also fell, down 0.8 percent against the dollar to $1.4571 and 1 percent at 116.40 yen after German exports posted their biggest drop in more than two years in April and industry output fell 0.6 percent, confounding expectations for an unchanged reading. For more, see [ID:nLDE7570B7] [ID:nLDE75706Q]

Greece needs substantial fresh aid from the euro zone to avoid the currency bloc's first state insolvency, a German newspaper reported on Tuesday, citing German Finance Minister Wolfgang Schaeuble. [ID:nB4E7G900O]

The cost of insuring Greek and Portuguese debt against default rose, while the premium investors demand to hold Greek, Portuguese and Irish government bonds rather than benchmark German Bunds also increased.

U.S. government bonds rose despite a Fitch Ratings warning that the United States probably would not be able to maintain its prized AAA sovereign ratings status if it suffered even a "technical" default on its debt. Investors were instead focused on a sputtering economic recovery.

U.S. benchmark Treasury yields fell back below the key 3 percent level as worries over the tepid pace of economic growth spurred investors to buy lower-risk assets.

Yields on 10-year notes were last at 2.97 percent, down from 3.00 percent late on Tuesday. The yield on 10-year U.S. paper was 9 basis points below that of 10-year German Bunds, the widest spread in a month. (Additional reporting by Edward Krudy and Steven C. Johnson in New York, and Neal Armstrong, Harpreet Bhal, Nick Macfie, Brian Gorman and Kirsten Donovan in London; Editing by Dan Grebler)