As many as three million people have rallied in cities across Brazil calling for president Dilma Rouseff's impeachmen over alleged fiscal mismanagement and low approval ratings.

The country is amid an investigation into corruption at oil giant Petrobas that involves the former president as well as key figures from Rouseff's inner circle.

Investigators have been looking into claims that former President Lula da Silva benefited from illegal kickbacks at Petrobras when he was in power.