CURITIBA, Brazil — Several thousand people have protested the jailing of former President Luiz Inacio Lula da Silva in the southeastern Brazilian city where he is serving a sentence for corruption.

At least 6,000 protesters marked Tuesday's Labor Day holiday by calling attention to what they say is the unfair imprisonment of the former union leader in the city of Curitiba.

Music groups performed and politicians spoke. Many protesters wore red, the color of da Silva's Workers' Party, and carried signs calling for the former president to be freed or urging the ouster of the judge who convicted him.

Da Silva began serving his sentence in April after he was convicted amid Brazil's corruption investigation. He denies wrongdoing and says the charges were concocted to prevent him from running in October's presidential elections.