BRASILIA, Aug. 14 (Xinhua) -- Some 5,000 members of Brazil's Landless Workers' Movement (MST) rallied in downtown Brasilia on Tuesday in support of ex-President Luiz Inacio Lula da Silva.

The demonstration came a day before Lula's left-leaning Workers' Party (PT) is due to register Lula as its candidate in October 7 presidential elections.

Brazil's Superior Electoral Court (TSE) may reject his candidacy, citing his conviction on charges of corruption. Lula is currently serving a 12-year jail sentence, but his appeals process continues.

The so-called "Free Lula" march kicked off on Saturday, with landless peasants setting out on foot from three different locations for a 50-kilometer march towards the capital.

PT's president, Senator Gleisi Hoffmann, on Monday confirmed the party will register Lula by the Wednesday deadline along with his running mate, the former mayor of Sao Paulo, Fernando Haddad.

At the same time, party faithful are set to gather outside the TSE's headquarters, along with members of the MST, the Unified Workers' Central (CUT), and other leading labor groups.

Brazil's Clean Record Law bars anyone convicted of a crime from running for elected office, but Lula supporters argue the popular leftist leader is a victim of political persecution designed to keep him out of the race.