RIO DE JANEIRO: Embattled Brazilian President Dilma Rousseff called a meeting with her closest advisers and congressional leaders on Monday, a day after nationwide demonstrations urging her ouster brought millions of people into the streets.

With an estimated 3 million people thought to have taken part in more than 100 protests nationwide, Brazil's top newspapers hailed Sunday's events as the largest political demonstrations in the country's history and said they'd succeeded in further complicating Rousseff's already difficult situation. Rousseff is fighting impeachment proceedings in Congress amid the worst recession in decades and a sprawling corruption investigation that has closed in on key figures in her Workers' Party.

The Folha de S. Paulo daily said Sunday's anti-Rousseff demonstrations were larger than mass protests in 1984 demanding direct presidential elections amid the country's military dictatorship.

"Surprised by the strong turnout on Sunday, the government has been put on alert that it needs to act quickly" to avoid Rousseff's impeachment, a report in Folha said Monday.

Rousseff's meeting Monday morning in the Planalto presidential palace was seen as an attempt to plot a way forward and secure congressional support that will be necessary to halt impeachment proceedings. Lower house Speaker Eduardo Cunha, a Rousseff foe, is expected to form a commission to begin impeachment proceedings sometime this week.

In a statement Monday, the US-based Eurasia Group political and economic risk consulting firm rated at 65 percent the probability that Rousseff will not serve out her term, which ends in 2016.

"We now think an impeachment vote will occur by May, and Rousseff will not survive it," the statement said.

Last week, Rousseff categorically ruled out resigning, saying it was objectionable to demand the resignation of an elected president without concrete evidence the leader had violated the constitution.

The demonstrations, overwhelmingly comprised of the white, older middle-class people who have railed against Rousseff for years, may have weakened the government. But they don't seem to have strengthened the opposition. The crowd in Sao Paulo, where the respected Datafolha polling agency estimated turnout at half a million people, booed opposition politician Aecio Neves, who narrowly lost to Rousseff in the 2013 presidential run-off.

While many were bracing for violence during Sunday's protests, no major incidents were reported. In a statement late Sunday, the government highlighted "the peaceful character" of the demonstrations, saying they underscored "the maturity of a country that knows how to co-exist with different opinions and knows how to secure respect to its laws and institutions."