(Adds close of U.S. markets)
* U.S. stocks rise on takeover, rising oil shares
* Oil rises on renewed Iran tension, Brazil strike threat
* Dollar falls versus euro as credit worries sweep markets
* Aluminum hits all-time high on Chinese output cut
By Herbert Lash
NEW YORK, July 10 (Reuters) - U.S. stocks rose on Thursday on reassuring testimony by Federal Reserve Chairman Ben Bernanke, who helped calm investors buffeted by credit worries and volatile trading, and optimism over a $15.3 billion takeover in the chemicals sector.
Worries about the health of mortgage lenders Fannie Mae and Freddie Mac, and investment bank Lehman Brothers, rattled investors and led stock and bond prices up and down all day.
Adding to anxiety, oil prices jumped nearly $6 a barrel amid threats to production in Nigeria and Brazil and another missile test by Iran that escalated tensions with the West.
A bright spot in another difficult day for financial stocks on Wall Street was Dow Chemical Co's <DOW.N> announcement it would buy rival Rohm and Haas Co for $15.3 billion.
The deal, which sent Rohm & Haas <ROH.N> shares up 64 percent to $73.62, is backed by Warren Buffett's Berkshire Hathaway <BRKa.N> and the Kuwait Investment Authority.
The Dow Jones industrial average <
> closed up 81.58 points, or 0.73 percent, at 11,229.02. The Standard & Poor's 500 Index <.SPX> was up 8.70 points, or 0.70 percent, at 1,253.39. The Nasdaq Composite Index < > was up 22.96 points, or 1.03 percent, at 2,257.85.A rise in oil heavyweights Exxon Mobil <XOM.N> and Chevron <CVX.N> also boosted U.S. stocks.
Spot gold prices <XAU=> rose $19.20 to $946.95 an ounce.
The continuing weakness of financial stocks, though, pushed investors to make safety bids for government debt during the day although bond prices slipped after stocks rallied late in the session.
Bernanke and Treasury Secretary Henry Paulson told Congress the Fed should get a stronger hand in supervising investment banks to help shield the economy from problems like the ones that forced the emergency rescue of Bear Stearns in March.
Bernanke said authorities are working within their existing authority to settle markets roiled by a credit crunch.
"Bernanke and Paulson are in essence trying to calm the market," said Bucky Hellwig, senior vice president at Morgan Asset Management, in Birmingham, Alabama.
Uncertainty over whether Fannie Mae <FNM.N> and Freddie Mac <FRE.N>, the two largest mortgage lenders, would need to raise enormous amounts of new capital soured early trading.
Former St. Louis Federal Reserve President William Poole stoked concerns by saying the two companies were "insolvent" and may need a U.S. government bailout, Bloomberg News said.
Fannie and Freddie were down about 14 percent and 21 percent, respectively, having pared losses that had pushed the shares far lower earlier in the session.
Capital-raising would dilute the value of current Fannie and Freddie shareholdings.
Also driving volatility was Lehman Brothers <LEH.N>, which was hit by later-denied talk that bond fund Pimco was reducing business with the bank. A Lehman spokesman declined to comment; Pimco said the company continued to trade with Lehman.
Lehman fell more than 13 percent.
"A lot of eyes are on Lehman at the moment. That's the kind of thing that puts the fox in the hen coop as far as the financials are concerned," said Jeremy Batstone-Carr, head of private client research at Charles Stanley in London.
"One thing is pretty certain and that is that we are some distance from the financial sector being out of the woods," Batstone-Carr said.
In a sign of market volatility, oil and banking shares led European stocks to fall more than 2 percent, but oil and to a lesser extent banking stocks helped lift U.S. indexes.
In Europe, the oil sector topped the losers and took 3.5 points off the pan-European index.
The pan-European FTSEurofirst 300 index <
> ended down 2.1 percent at 1,156.98 points.In the United States, the S&P Energy Index <.GSPE> rose 2.68 percent.
U.S. government debt fell. The benchmark 10-year U.S. Treasury note <US10YT=RR> fell 2/32 to yield 3.81 percent. The 30-year U.S. Treasury bond <US30YT=RR> fell 6/32 to yield 4.42 percent.
U.S. crude <CLc1> settled up $5.60 at $141.65 a barrel, off an earlier high of $142.10 a barrel. London Brent crude <LCOc1> settled $5.45 higher at $142.03 a barrel.
The dollar was dragged down by persistent worries over the health of U.S. financial sector.
The dollar fell against major currencies with the U.S. Dollar Index <.DXY> down 0.10 percent at 72.492. Against the yen, the dollar <JPY=> rose 0.23 percent at 107.00.
The euro <EUR=> added 0.27 percent at $1.5783.
Major Asian stock indexes cut early losses as banks gained on expectations recent falls had been too severe, while more stable oil prices eased some recent inflation concerns.
Shares of companies in the Asia-Pacific region excluding Japan <.MSCIAPJ> fell 0.2 percent on the day.
Japan's Nikkei share average <
> erased earlier falls to post a 0.1 percent gain. (Reporting by Gertrude Chavez-Dreyfuss, Ellen Freilich in New York and Jane Merriman, Jan Harvey and Rebekah Curtis, Anna Stablum and David Sheppard in London (Reporting by Herbert Lash. Editing by Richard Satran)