About 1,500 people have been held in Brazil after supporters of ex-President Jair Bolsonaro stormed Congress, the presidential palace and the Supreme Court in the capital Brasília.
The rioting came a week after President Luiz Inácio Lula da Silva was sworn in.
He condemned the “terrorist acts” and vowed to punish the perpetrators.
Mr Bolsonaro has not admitted defeat in October’s tight election that divided the nation, and flew to the US before the handover on 1 January.
On Monday, he was admitted to hospital in Florida with abdominal pain.
Tens of thousands of people are now demonstrating in Brazil’s largest city São Paulo in support of democratic values.
The turnout is impressive – a part of Paulista Avenue, Brazil’s most famous street, is blocked off – as crowds have filled the area, singing, dancing and chanting for justice, reports the BBC’s Katy Watson in São Paulo.
There was however a huge police presence in case of any trouble. At times, the atmosphere has felt tense, our correspondent adds.
The new president – widely known as Lula – and the heads of Congress and the Supreme Court said they “reject the terrorist acts and criminal, coup-mongering vandalism that occurred” during Sunday’s riots.
The dramatic scenes saw thousands of protesters clad in yellow Brazil football shirts and flags overrun police and ransack the heart of the Brazilian state.
Lula was forced to declare emergency powers.
On Monday morning, heavily armed officers started dismantling a camp of Mr Bolsonaro’s supporters in Brasília – one of a number that have been set up outside army barracks around the country since the presidential election.
Watch: Ros Atkins on… Why the Brazil riots happened
Authorities arrested 1,200 people on Monday – in addition to 300 detained a day earlier.
Justice Minister Flavio Dino said some 40 buses which had been used to transport protesters to the capital had been seized.
The scale of the damage was still starkly evident on Monday afternoon, even as officials lauded the progress of the clean-up at the presidential palace, reports the BBC’s Bernd Debusmann in Brasília.
He says workers were cleaning up broken glass around the building’s exterior. Almost every window on the building’s ground floor had been damaged, forcing crews to painstakingly remove each pane of glass and replace it with a new one.
The cobblestone pavement outside the palace also showed signs of damage, with large patches torn out by rioters on Sunday.
“They were using the rocks as missiles,” one official said. “To break the glass.”
In the nearby Congress building, the damage included valuable works of art, including several high-profile pieces that were reportedly damaged by water or defaced during the riot.
The streets, however, were largely calm and devoid of noticeable military or police presence, our correspondent adds.
Mr Bolsonaro condemned the attack and denied responsibility for encouraging the rioters in a post on Twitter some six hours after violence broke out.
Meanwhile, Brasília Governor Ibaneis Rocha has been removed from his post for 90 days by the Supreme Court.
Justice Minister Alexandre de Moraes accused him of failing to prevent the riot and of being “painfully silent” in the face of the attack. Mr Rocha has apologised for Sunday’s events.
