Brazil's former president Jair Bolsonaro, on trial over a botched coup bid and under house arrest since August, was taken into custody on Saturday, according to his lawyer and a court document.

The far-right firebrand was sentenced in September to 27 years in prison over a plot to stop leftist Luiz Inacio Lula da Silva from taking office in 2022 following Bolsonaro's election defeat.

The Supreme Court judge leading the trial against Bolsonaro, Alexandre de Moraes, concluded Bolsonaro was a "high flight risk" and ordered pre-trial detention.

The ruling says Bolsonaro planned to break his ankle monitor during a rally on Saturday called by his son outside the politician's home in Brasilia.

Sources close to the case earlier said the former leader had been taken into custody as a precaution and not to begin serving his sentence.

Celso Vilardi, one of Bolsonaro's lawyers, said "he has been imprisoned, but I don't know why."

A police statement that did not mention the former president by name said officers had "executed a preventive arrest request in compliance with a Supreme Court decision."

Bolsonaro, who governed Brazil from 2019 to 2022, was placed under house arrest in August for violating measures imposed on him.

He has been confined to an upscale condominium in the capital Brasilia, and monitored electronically.

An appeal of his sentence was rejected last week, bringing him one step closer to serving his prison term.

Bolsonaro's lawyers have said they would file further appeals before a Monday deadline, but sought to get ahead of plans to put Bolsonaro in jail by requesting he be allowed to serve his sentence under house arrest.

They had previously argued that Bolsonaro's medical needs were "absolutely incompatible with a common prison environment."

Bolsonaro was convicted in September of leading a criminal organization that conspired to ensure his "authoritarian hold on power."

The plot involved a plan to assassinate Lula, his vice president Geraldo Alckmin, and the Supreme Court judge de Moraes. (AFP)