With Lula no longer on the run, the chances of right-wing candidates winning the elections increase significantly, as the left has no other contender nearly as strong as Lula, according to political analysts.

In the end, Lula told supporters to keep fighting, saying that "We are an idea. And they cannot arrest the dream."

Following the nearly hour-long speech, his supporters locked hands and surrounded the union building to block his departure and prevent the police from entering.

Later, Lula was seen getting into a car that was presumably going to take Lula to the police, with his lawyer Cristiano Zanin.

He later exited on foot, was taken into custody and driven to the Congonhas airport in the state capital Sao Paulo, from where he is to fly to Curitiba, capital of southern Parana state.

Parana is where prosecutors have led Brazil's wide-reaching investigation into graft involving state oil giant Petrobras and other companies. Code named Operation Car Wash, the investigation has led to numerous high-level arrests.