Images on TV channel Globo News showed protesters roaming the presidential palace, many of them wearing green and yellow, the colors of the flag that have also come to symbolize the Bolsonaro government.

The incidents recalled the Jan. 6 invasion of the U.S. Capitol, something many political analysts and the judiciary Bolsonaro have warned about for months. But in this case it is likely that Congress and the Supreme Court had limited personnel inside the buildings on a Sunday.

Bolsonaro supporters have been protesting against Lula's electoral win since Oct. 30, blocking roads, setting vehicles on fires and gathering outside military buildings, asking armed forces to intervene. Many believed election results were fraudulent or unreliable.

"This absurd attempt to impose their will by force will not prevail,'' said Justice Minister Flavio Dino on his Twitter account. "The government of the Federal District has ensured there will be reinforcements. And the forces at our disposal are at work.''

Senate President Rodrigo Pacheco said he was in permanent contact with Brasilia's governor, Ibaneis Rocha, and that the entire police apparatus had been mobilized to control the situation.

Bolsonaro, who flew to the U.S. ahead of Lula's inauguration, has not yet condemned or commented on the ongoing situation.