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By Vanessa Buschschlüter
BBC News
Supporters of Brazil's outgoing far-right president, Jair Bolsonaro, tried to attack the headquarters of the federal police in Brasilia on Monday.
Tension escalated after police arrested a pro-Bolsonaro indigenous leader.
Mr Bolsonaro was defeated in last month's election by his left-wing rival, Luiz Inácio Lula da Silva, but some of his supporters refuse to recognise the president's defeat.
They set alight several vehicles and blocked a number of roads, police said.
Police said the protesters "attempted to invade" the federal police building, where José Acácio Serere Xavante was being held.
Supreme Court Justice Alexandre de Moraes had ordered that the indigenous leader be detained for 10 days for "alleged anti-democratic acts".
According to prosecutors, José Acácio Serere Xavante had "attempted to incite people to try to abolish the rule of law and to impede the swearing-in of the president and vice-president elect".
Prosecutors did not provide details as to how the indigenous leader had tried to impede the handover of power, which is scheduled for 1 January.
Mr Serere Xavante released a video from detention calling on people who had gathered outside the police HQ to "refrain from engaging in conflict, fights or confrontations" with the police force.
"What sadly occurred, the destruction of cars and the attack on the police HQ, can't carry on," he added.
Police fired tear gas and rubber bullets to disperse the protesters. Firefighters said five buses and eight cars had been set on fire. A number of key roads remained closed on Tuesday morning.
The president of the Senate, Rodrigo Pacheco, said the "vandalism" had been caused by "an angry minority".
The incident happened shortly after Brazil's electoral commission had certified Luiz Inácio Lula da Silva as the official winner of October's presidential poll.
Mr Bolsonaro has still not conceded defeat but a challenge brought by his party has been dismissed.
The commission also dismissed unsubstantiated allegations by supporters of Mr Bolsonaro that Lula's election win had been fraudulent.
Lula, who won the election run-off by a margin of 1.8 percentage points last month said in an emotional speech that democracy had won in spite of attempts by President Bolsonaro to discredit the electoral system.