Thousands of pro-democracy demonstrators have taken to the streets of the Brazilian city of Sao Paulo to denounce the riots and storming of key government buildings by supporters of the ultra-right-wing former president Jair Bolsonaro.
Demonstrators carried signs with messages such as "Democracy forever", as well as banners reading "We are with Lula and for democracy" and "Respect for the people's vote."
Young people, labor union activists, and anti-racism advocates were among the protesters, who demanded stringent punishment for rioters.
On Sunday, Bolsonaro's rioting supporters ransacked the presidential palace, the Supreme Court and the Congress. The riots capped months of tension following the October 30 presidential vote that Bolsonaro lost to Luiz Inacio Lula da Silva.
Observers have compared the raids to the January 6, 2021 insurrection at the US Capitol building by supporters of then-US president Donald Trump, a Bolsonaro ally, and have termed the situation as a serious episode of "political unrest."
Police arrested 300 over the attack on Sunday, while 1,200 others were detained on Monday as security forces dismantled an improvised camp of Bolsonaro's supporters outside the army's headquarters in Brasilia.
Lula denounced far-right "acts of terrorism" as he met the leaders of both houses of Congress and the head of the Supreme Court on Monday.
"The three powers of the republic, the defenders of democracy and the constitution, reject the terrorist acts and criminal, coup-mongering vandalism that occurred," they said in a joint statement, adding that they were taking legal measures.
He toured the wreckage of his presidential palace on Monday and ordered the federal government to take control of policing in the capital Brasília.
Lula on Sunday blamed Bolsonaro, who is now hospitalized in a hospital in the US, for instigating his supporters after a campaign of baseless allegations about the election result, vowing to bring those responsible for the "fascist" assault to justice.
The leftist president declared federal intervention in public security in the capital lasting until January 31.
He said the local militarized police force that reports to Brasilia Governor Ibaneis Rocha, a former Bolsonaro ally, did nothing to stop the advance of the protesters.
Brazil Supreme Court Justice Alexandre de Moraes suspended Rocha from office alleging security flaws that allowed the invasion of government buildings.
The attack was the worst on the country's institutions since democracy was restored four decades ago.
The Bolsonaro-allied fanatics refuse to accept his narrow defeat during October's presidential elections against 77-year-old Lula.
Lula was sworn in on January 1, unleashing a barrage of rebuke against Bolsonaro for, what he called, his predecessor's egregious mishandling of the country's affairs during his mandate.
Bolsonaro, dubbed the "Tropical Trump", has questioned the credibility of the country's electronic voting system without providing evidence.
He fled Brazil to the US state of Florida two days before the end of his mandate, reportedly to avoid going through the ceremonial handing over of the presidential sash to Lula.
Bolsonaro on Sunday condemned the "pillaging" in Brasilia, but rejected claims that he incited the riots, and defended the right to "peaceful protests."