Hundreds of thousands of Brazilians marched peacefully Sunday in over 50 cities around the country to demand President Dilma Rousseff's impeachment and to criticize government corruption.

The biggest protests were in Sao Paulo, an opposition stronghold where hundreds of thousands gathered on a main avenue, as well as in the capital city of Brasilia and in Rio de Janeiro.

Dozens of cities saw demonstrations gathering together a few thousand people each. According to the website of the Globo TV network, Brazil's largest, the total number in the streets across Brazil was more than 300,000 people, based on local police estimates.

"We are here to express our indignation with the government-sponsored corruption and thieving, and to demand Dilma's impeachment," said Andre Menezes, 35, protesting with hundreds of thousands on Avenida Paulista in Sao Paulo.

"She may have not been directly involved in the corruption at [state-run oil company] Petrobras, but she certainly knew about it, and for me that makes her just as guilty and justifies her ouster," he added.

Calls for a military coup

In Rio, police estimated 15,000 people marched along the golden sands of Copacabana beach, where they waved Brazilian flags and many openly called for a military coup to dissolve the government.

A demonstrator wears a sticker that reads in Portuguese 'Dilma out' during a march demanding the impeachment of Brazil's President Dilma Rousseff in Sao Paulo, Brazil, on Sunday. (Andre Penner/Associated Press) "I don't want my country to turn into a Venezuela, we don't want an authoritarian government!" said Marlon Aymes, 35, helping carry a six-metre banner that read in English: "Army, Navy and Air Force. Please Save Us Once Again of Communism."

"We want the military to dissolve Congress and call new elections, because the level of corruption is too widespread to do anything else," Aymes added.

Much protester anger was focused on a kickback scheme at Petrobras, which prosecutors call the biggest corruption scheme ever uncovered in Brazil. At least $800 million US was paid in bribes and other funds by the nation's biggest construction and engineering firms in exchange for inflated Petrobras contracts.

Top executives are already in jail and the attorney general is investigating dozens of top congressmen, along with current and former members of the executive branch, for alleged connections to the scheme that apparently began in 1997 before Rousseff's party took power in 2003.

''I don't want my country to turn into a Venezuela. - Protester Marlon Aymes

Rousseff, a former chairwoman of Petrobras's board, has not been implicated and so far is not being investigated, though top officials from her administration, including two former chiefs of staff, are caught up in the inquiry.

The marches add pressure on Rousseff, whose poll ratings have never been lower and who is facing dual economic and political crises. But the protests are significantly different than anti-government demonstrations in 2013. Those earlier protests cut across political, social and economic lines, and were a widespread expression of frustration with poor public services such as health care and transportation, as well as a cry against government corruption.

Sunday's protests, largely organized by ad-hoc right-leaning groups over social media, appeared far more politically focused, and demonstrators came from social classes that voted against Rousseff in her narrow re-election in October.