SAO PAULO/RIO DE JANEIRO, Aug 10 (Reuters) - Brazilian state-run oil company Petrobras is not planning to sell its 36% stake in petrochemical firm Braskem, newspaper Valor Economico reported on Thursday, citing unnamed sources.

Petrobras is one of Braskem's main shareholders alongside conglomerate Novonor, which holds a controlling stake in the firm but has sought to sell it to repay creditors after entering bankruptcy protection.

According to Valor Economico, Petrobras CFO Sergio Leite said during a meeting with analysts that the company has no plans to sell off its stake in Braskem.

In a statement, the company said it was studying alternatives in the petrochemicals sector as part of its strategic planning. It did directly comment on the report.

Petrobras holds contractual rights to buy out Novonor's stake in the firm or exercise tag-along rights in case of a potential sale.

Three offers so far have been presented to take control of Braskem: a joint bid from Abu Dhabi's ADNOC and U.S. asset manager Apollo, and separate proposals from Brazilian firms Unipar Carbocloro and J&F.

Following Valor Economico's story, shares of Braskem rose 7.8% in afternoon trading, making it one of the top gainers on Brazil's benchmark stock index Bovespa. (Reporting by Marta Nogueira and Paula Arend Laier; Writing by Carolina Pulice; Editing by Cynthia Osterman)