RIO DE JANEIRO (AP) -- Uncertainty clouded Brazil's already turbulent political scenario Thursday as a judge blocked the appointment of former President Luiz Inacio Lula da Silva as chief of staff to his successor just moments after his tumultuous swearing-in ceremony.

Critics of current President Dilma Rousseff accuse her of a transparent maneuver aimed at helping the once wildly popular Silva slalom legal woes that saw him taken in for questioning in a sprawling corruption probe less than two weeks ago. Cabinet members cannot be investigated, charged or imprisoned unless authorized by the Supreme Court.

Rousseff has insisted the Cabinet appointment has nothing to do with the former president's legal problems, saying Silva would help put the country back on track economically and spearhead the fight against attempts to oust her over allegations of fiscal mismanagement. The impeachment process moved a step closer Thursday as the lower house established a special commission on the matter.

As the spectacle continued to play out, the simmering anger that bought an estimated 3 million people onto the streets in nationwide anti-government demonstrations over the weekend again spilled over, with protests flaring in Brasilia and Sao Paulo, where demonstrators brandished inflatable dolls of Silva in black-and-white prison stripes. A pro-Silva rally was slated for Friday, but it was not clear whether the former leader would attend.

Rousseff went on the offensive at Thursday's swearing-in ceremony, calling those pressing for her removal "putschists" and accusing Sergio Moro, the judge who is leading the corruption probe at the state-run oil company Petrobras, of violating the constitution and acting in a partisan manner.

"Shaking Brazilian society on the base of untruths, shady maneuvers, and much-criticized practices violates constitutional guarantees and creates very serious precedents," Rousseff said. "Coups begin that way."

The injunction suspending Silva's nomination, brought by a federal judge in Brasilia, was widely expected as such tactics are often used to delay or interrupt political appointments and decisions. But the practical effects remain subject to debate, with some attorneys insisting Silva is the chief of staff -- and enjoys the special legal standing afforded by the role -- while others contended the injunction must first be ruled on by a higher court.

Gustavo Binenbojm, a law professor at Rio de Janeiro's state university, insisted the injunction is "valid until it's overruled," meaning that Silva is not yet a Cabinet minister.

"The government can't ignore it," said Binenbojm. "The government can try to overrule it, and I think that would be a slam dunk."

On the other hand, Brasilia-based attorney Joaquim Pedro Rodrigues said the injunction stipulates that if the swearing-in already took place, the suspension would not take effect until a final decision is reached. While Silva won't be able to exercise official functions until the matter is resolved, he will enjoy the Cabinet ministers' special legal standing until then, Rodrigues said.

Solicitor General Jose Eduardo Cardozo, a close ally of Rousseff's, said "political motivations" were behind the injunction, which he called "absolutely inappropriate."

"The situation is absurd," Cardozo said at a news conference, adding that the government has appealed. He attacked the judge who issued the injunction as partisan, citing recent photos posted on Facebook showing him at an anti-government rally.

Both Rousseff and Silva have repeatedly denied any wrongdoing, but Rousseff has seen her popularity nosedive as the country of 200 million has spiraled into crisis after crisis.

The Petrobras corruption investigation has stained Brazil's political and business elite. The country is ground zero for the Zika virus, which scientists believe can lead to birth defects. The economy is mired in the worst recession since the 1930s, with rising inflation and daily announcements of layoffs adding to people's fears and desperation. And in the middle of it all, Brazil is set to host the Summer Olympics in Rio de Janeiro in August.

At Thursday's swearing-in ceremony, the atmosphere recalled a campaign rally as a crowd packed with top officials broke into pro-government chants.

In a combative speech, Rousseff said she was counting on Silva, her "great friend, great comrade," to help lift the country out of the current economic and political imbroglios.

She lashed out at Wednesday's surprise release of tapped phone calls between Silva and a host of prominent public figures, including Rousseff herself. Judge Moro released the recordings hours after the announcement of Silva's appointment, saying that the taps appeared to suggest attempts to influence judicial officials in Silva's favor.

Rousseff called the recordings illegal and said their release made "clear the attempt to overstep the limits of the democratic state."

Moro compared the situation to a U.S. Supreme Court ruling in the Watergate scandal that toppled President Richard Nixon.

"Not even the highest authority of the republic has absolute privilege of protection of their communications," Moro wrote, adding that the 1974 decision in the U.S. vs Nixon case was "an example to be followed."

On Thursday, Rousseff's nemesis, lower house speaker Eduardo Cunha established the committee that will decide whether to proceed with impeachment steps against her. Raucous celebrations broke out on the floor, with opposition representatives brandishing signs reading "impeachment now" as Rousseff allies chanted "there won't be a coup!"

Still, it was an early step in a drawn-out process that involves multiple votes in the lower house as well the Senate. Analysts have said the impeachment process could take months, should it move forward.