Supporters of Brazilian President Dilma Rousseff called mass street rallies in her defence on Friday in over 30 cities, as she is facing a political crisis amid corruption charges and anti-government protests.
Former president and Rousseff’s predecessor Luiz Inacio Lula da Silva or "Lula" was sworn in as her chief of staff on Thursday, which led to angry protests as it could give Lula some immunity from ongoing bribery prosecutions related to Petrobras.
Police used tear gas to disperse hundreds of protesters who clashed with Lula's leftist supporters outside the presidential palace later in the day.
Around three million people joined anti-government demonstrations last weekend.
The biggest counter demonstrations are expected on Friday in Sao Paulo, Rio de Janeiro and Brasilia, called by Rousseff's Workers' Party, the major trade union CUT and other groups.
On Thursday, Congress also started proceedings to impeach the president on allegations - unrelated to Petrobras - that she broke budget rules to boost spending in her election campaign in 2014.
A 65-member impeachment committee will study if there are grounds to try her in the Senate.
As the Petrobras probe reaches Rousseff's inner circle, Rousseff appointed Lula, one of Brazil's most influential politicians, in an effort to fight impeachment and win back working-class supporters amid the worst economic recession in decades.
Lula became a hero for many of Brazil's poor after millions of people came out of poverty between 2003 to 2010 when he led the government.
However the corruption probe has weakened Lula's sway in Congress and there are growing signs that the main coalition partner of Rousseff's party may abandon her government.
A judge in Brasilia has issued a ruling suspending Lula’s appointment of Lula on the grounds it prevented "the free exercise of justice."
That ruling was overturned late Thursday on appeal, but a separate federal court in Rio de Janeiro upheld another lawsuit blocking the appointment.
Rousseff accused her enemies of mounting a "coup" against her.
Judge Sergio Moro, who oversees the investigation into the Petrobras scandal, publicised taped phone conversations on Wednesday suggesting Lula and Rousseff tried to influence prosecutors and courts in favour of the former president.
"The putschists' shouting won't make me veer from my path or bring us to our knees," Rousseff said as she was heckled at Lula's swearing-in.
"If they violate the rights of the president, what will they do with those of the citizens? That is how coups start."