Brasilia's public security officials said they had secured the area around Lula's hotel, and urged motorists to avoid the center of the city where many roads had been closed.
SPARKED BY ARREST
The violence in Brasilia came after Supreme Court Justice Alexandre de Moraes, who has led probes into Bolsonaro and his allies, on Monday ordered the temporary arrest of José Acácio Serere Xavante for allegedly carrying out anti-democratic acts.
Xavante, an indigenous leader, is among the Bolsonaro supporters who have protested in defiance of the Oct. 30 election result.
"I cannot accept criminals reigning in Brasil," Xavante tweeted last month. "Lula cannot be certified."
Last week, Bolsonaro broke weeks of post-election silence to say that his situation "hurts my soul."
"Who decides where I go are you. Who decides which way the armed forces go are you," Bolsonaro told his supporters at the gates of the presidential residence on Friday.
In a statement, the Supreme Court said Moraes "decreed the temporary arrest, for 10 days, of the indigenous José Acácio Serere Xavante, due to evidence of the commission of crimes of threat, persecution and violent abolition of the Democratic State of Law."
It said Xavante had led protests across Brasilia and had used "his position as chief of the Xavante people to enlist indigenous and non-indigenous people to commit crimes," threatening Lula and Supreme Court justices.
Xavante had "expressly summoned armed people to prevent the certification of elected" politicians, the statement added.
