Brazil's capital has prepared for the possibility of more violent demonstrations by people seeking to overturn the presidential election, with local security officials blocking access to buildings trashed four days earlier by a horde of rioters.

A flyer promoting a "mega-protest to retake power" circulated on social media platforms on Wednesday, particularly Telegram, and urged protesters to turn out in two dozen cities, including the capital.

It was unclear how large or violent such demonstrations might shape up to be, but skittish authorities took no chances.

Speaking to journalists in Brasilia, the federal appointee who has assumed control of the capital's security said police were shutting down the main avenue to traffic and limiting pedestrian access with barricades.

They are blocking all access to the square that was the site of Sunday's mayhem, said the official, Ricarado Cappelli.

He said a small area on the avenue has been reserved for peaceful demonstrations, but will be surrounded by police and the national guard and all protesters will be searched upon entry.

"The right to protest freely will always be respected and cannot be confused with terrorism," Cappelli said.

Citing the call to action on social media, a Supreme Court justice ordered local authorities in cities across Brazil to prevent protesters from blocking roads or occupying public spaces and buildings. 

Justice Alexandre de Moraes also ordered arrests and fines for people and companies who participate or help with logistics and funding.

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Nation on edge 

The nation remains on edge after supporters of far-right ex-president Jair Bolsonaro rampaged through Congress, the Supreme Court and the presidential palace on Sunday, laying ruin to the government's three most important buildings. 

Officials arrested or detained some 1,500 people by the following morning, hundreds of whom were sent to prison. Some 600 were released on "humanitarian grounds."

Demonstrations were also planned for Rio de Janeiro, Sao Paulo and other cities in a country left deeply divided by a vitriolic campaign for October elections in which leftist Luiz Inacio Lula da Silva narrowly beat Bolsonaro.

Though there is no evidence of fraud in the presidential election, the protesters have claimed the true winner was Bolsonaro. 

He has fired up his base about the vulnerability of electronic voting machines despite independent experts' assurances they are closely scrutinised. 

Bolsonaro also has warned his supporters that the election's leftist victor, Lula da Silva, would impose communism.

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