Brazilian police have used tear gas on anti-government protestors in Sao Paulo ahead of pro-government rallies.
Protests against President Dilma Rousseff erupted in several cities two days ago after she appointed her predecessor, Luiz Inacio Lula da Silva, as a minister.
President Rousseff is accused of shielding Lula from charges of money-laundering, which he denies.
Protesters have called for President Roussef to be impeached.
They have accused her of economic mismanagement and involvement in a sprawling corruption scandal in the state oil company, Petrobras.
President Rousseff insisted that she appointed Lula, who had started to make overtures to stand for president in 2018, to help her rebuild her political base in Congress and fight the impeachment proceedings.
A second injunction against Lula taking up his role as chief of staff was struck down by a court in Rio de Janeiro on Wednesday.
Lula is likely to face more legal challenges to him joining the government since anti-government protestors believe his appointment was made to grant him immunity from money-laundering charges that he denies.
If appointed as a a minister, any charges against him can only be dealt with by the Supreme Court, which operates more slowly.
An impeachment committee in the lower house of Congress held its first session Friday and said it expected to reach a decision within a month on whether to recommend removing the president.
The nationwide rallies on Friday are the first time that the government has massed the ranks of supporters since Lula was briefly arrested last week.
The government aims to prove the strength of its support among the poor majority of Brazilians after millions of people came out on the streets last week to protest against President Dilma Rousseff’s government and against corruption.