Just days after the attack on the presidential palace, Supreme Court and Congress by backers of far-right ex-president Jair Bolsonaro, Lula said the rioters likely had inside help.

He ordered a thorough staffing review, saying he was "convinced that the door of the Planalto (presidential) palace was opened for people to enter because there are no broken doors."

In a notice published in the official gazette Tuesday, it was announced that 40 soldiers have been removed from the presidential detail at Alvorada palace, where Brazil's presidents live.

Leftist Lula beat Bolsonaro by a razor-thin margin in October elections that followed a vitriolic and divisive campaign.

As he marked a week in office, thousands broke into the seats of power on January 8, smashing furniture, damaging priceless works of art and leaving behind graffiti messages calling for a military coup against Lula.

The president said last week that any "radical bolsonarista" found still working for the government would be dealt with, and cited media reports of alleged threats made by staffers inherited from the previous administration.

"How can I have a person outside my office who might shoot me?" asked Lula, who said members of the security services may have been involved in the uprising.

Bolsonaro, who left Brazil two days before Lula's inauguration and is in the United States, is being investigated on suspicion of instigating the uprising.

He has denied any link to the riots.

In a video published Monday, Bolsonaro expressed "regret" over the events, which he described as "unbelievable."