Aug 30 (Reuters) - Brazilian state-run oil company Petrobras said on Wednesday it signed a memorandum of understanding (MOU) with Chinese state-owned oil firm CNOOC to extend its collaboration in the energy sector.

In a securities filing, Petrobras said it has also signed a MOU with Asia's top refiner, Sinopec Corp, to collaborate in research in oil exploration and production in Brazil and abroad. (Reporting by Carolina Pulice and Peter Frontini; Editing by Leslie Adler)