RIO DE JANEIRO (NYTIMES) - Besieged by protests, Brazil's president on Wednesday deployed federal troops to restore order in the capital, Brasília, after demonstrators calling for his ouster clashed with security forces.

Defense Minister Raul Jungmann went on national television on Wednesday (May 24) afternoon to insist that President Michel Temer was only trying to restore calm in the capital by calling in the troops to patrol some areas.

One of the city's iconic modernist buildings, the Agriculture Ministry, was set on fire and other government buildings were vandalised during the mayhem. Regional officials in Brasília put the number of protesters on Wednesday at about 35,000.

"A protest that was supposed to be peaceful deteriorated into violence, vandalism and disrespect," Jungmann said.

While supporters of the move say the capital must remain calm and functioning, the use of the armed forces in Brazil touches a nerve among critics of the military dictatorship that ruled the country from 1964 to 1985, a period known for human rights abuses and the restriction of civil liberties.

Jairo Nicolau, a professor of political science at the Federal University of Rio de Janeiro, said the move to call in the armed forces was a "mistake."

"It is a bad sign at this moment; it could signal weakness from the government," Nicolau said. "We are in a moment of insecurity, and any act of this type creates more insecurity. We have had much worse demonstrations than this that were controlled by the police."

Tensions have been rising in Brazil over a scandal engulfing Temer's government, especially after a beef tycoon secretly recorded his discussion with the president about obstructing an anti-corruption drive.

The disclosure last week of the recording prompted a plunge in Brazil's financial markets, an investigation of Temer and widespread calls for him to resign, but he has combatively refused to step down.

Brazilian news organizations reported Wednesday that ministry buildings in Brasília were evacuated as a result of the protests, while a session of Congress was suspended after shouting matches erupted between opponents of Temer, 76, a centrist who has drifted to the right, and his supporters. Firefighters managed to control the blaze in the Agriculture Ministry.

The public security secretariat of Brazil's Federal District, which includes Brasília, blamed protesters trying to get through a security cordon for the violence.

"Demonstrators tried to invade the security perimeter," the secretariat said in a statement, but they were stopped by the police, "who used progressive force." Some demonstrators contested the official statement.

Vitor Guimarães, 26, an activist from the Landless Workers' Movement, a militant leftist group, said that he was on the grassy area in front of Congress when the police attacked protesters.

"The main part of the demonstration had not arrived and they started throwing percussion grenades, tear gas and rubber bullets," Guimarães said.

Some protesters hid behind shields, and others threw the grenades back at the police, he said.

"There were various focal points of resistance," Guimarães said. "People with shields wanting to get closer, and people throwing the bombs back and some letting off fireworks."

Guimarães was hit in the face by a projectile he said he thought was a tear-gas canister.

"The police wanted to expel everyone from the esplanade," he said.

In addition to the protests in Brasília, police officers in Rio de Janeiro came under attack by demonstrators wielding slingshots in the city's downtown, officials said. Lawmakers in Rio had been debating measures to ease the state's severe financial crisis.

Amid the impasse on the national level, Temer has also maintained pressure on Congress to vote on broadly unpopular austerity measures. A general strike already disrupted cities across Brazil in April when unions marshalled resistance to Temer's proposals, which would curb pension benefits and overhaul labour laws.

Temer has gone on the offensive against his accuser, Joesley Batista, 44, an heir to the JBS food processing empire. Temer claimed that the recording of their conversation in March had been adulterated and manipulated, and he said he would seek the suspension of the graft investigation into his activities.

Temer is accused of receiving millions in illicit payments and seeking to obstruct corruption inquiries. He took power barely more than a year ago after helping to orchestrate the ouster of his predecessor, Dilma Rousseff, over accusations that she manipulated the budget to conceal mounting economic problems.

Nicolau, the political science professor, said that while Temer remained in office, protests like those on Wednesday were likely to worsen.

"I see these demonstrations as a radicalisation that is going to get more serious," he said. "There is enormous dissatisfaction."