Up to a million people took to the streets across Brazil to protest against President Dilma Rousseff's administration, following a corruption scandal engulfing state-run oil firm Petrobras, coupled with a dismal economic outlook

Demanding impeachment of Rousseff, the protesters asserted that the president was aware of large-scale corruption at Petrobras.

About 500,000 people hit the streets in Sao Paulo, as Brazil marks the 30th anniversary of its return to democracy from military rule. Tens of thousands took part in rallies in capital Brasilia, Rio de Janerio and Porto Alegre.

However, Rousseff, who came to power for a second term five months ago, is unlikely to be impeached, according to reports.

"We are here to express our indignation with the government-sponsored corruption and thieving, and to demand Dilma's impeachment. She may have not been directly involved in the corruption at Petrobras, but she certainly knew about it, and for me that makes her just as guilty and justifies her ouster," Andre Menezes, 35, protesting on Avenida Paulista in Sao Paulo told the Associated Press.

Dilma's woes have been compounded by the plunging currency; the economy has been facing stagnation for the fifth consecutive year, fuelling anger among people.

Authorities have been cautious in their response to the protests. Rousseff's cabinet members have said the protesters have been instigated by opposition parties, who lost the elections. However, the authorities have been forced to recognise people's right to take to the streets, as an "expression of democracy".

Meanwhile, the government has pledged to take forward a series of measures to curb corruption.