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.
