BUZZ-U.S.-listed Brazilian stocks: Poll shows opposition closing gap
** Petróleo Brasileiro SA's shares up 4.6 pct at $16.77, steelmaker Companhia Siderurgica Nacional up 9.2 pct at $5.18, Banco Bradesco SA up 4.4 pct at $15.43
** Poll shows President Dilma Rousseff and opposition candidate Aecio Neves tied in a possible second-round vote in October
** Investors accuse Rousseff's government of intervening excessively in economy
** Companhia Siderurgica Nacional launches share buyback
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