RIO DE JANEIRO, Jan. 23 (Xinhua) -- Security was tightened in the Brazilian city of Porto Alegre on Tuesday, a day ahead of the appeal trial of Brazil's former president Luiz Inacio Lula da Silva.

Additional law enforcement forces have been flooding into the city over the past few days, while road blocks were put in place to keep crowds away from the courthouse.

Planes are to be banned from flying over the building on Wednesday and even sharpshooters will be positioned on nearby rooftops.

Authorities designated two separate areas for pro- and anti-Lula protesters to gather.

In the area designated for supporters of the Workers' Party (PT) leader, thousands of people were already camping out as dozens of buses showed up, packed with admirers, some from far away states.

The PT has been charged with corruption and Lula has been convicted of accepting bribes in the form of an upscale beachfront apartment in Guaruja, in Sao Paulo state.

Wednesday's trial will uphold or throw out that conviction, and potentially determine whether he will be eligible to run in upcoming presidential elections scheduled in October 2018.