RIO DE JANEIRO (Reuters) - Former Brazilian leader Luiz Inacio Lula da Silva will face a fifth corruption trial, a judge ruled on Monday, as charges pile up against the man seen as a front-runner to win the 2018 presidential election.

Brazil's former president Luiz Inacio Lula da Silva attends the funeral of Cardinal and Archbishop of Sao Paulo Dom Paulo Evaristo Arns at Se Cathedral in Sao Paulo, Brazil, December 15, 2016. REUTERS/Leonardo Benassatto

Judge Sergio Moro, who has overseen the bulk of Brazil’s biggest graft probe into a long-standing kickback scheme at state-run oil company Petrobras, ruled that Lula, his wife Marisa and seven others will stand trial.

The latest case involves the acquisition of land that was to be used for the Lula Institute, the 71-year-old leftist politician’s think tank, along with an apartment in a Sao Paulo suburb.

Prosecutors allege that Latin America’s biggest construction firm, Odebrecht, paid 12.9 million reais ($3.8 million) for the land and the apartment as a bribe to Lula in exchange for public contracts.

In an email, the ex-president’s lawyers said Lula was innocent of the charges.

Lula is already facing a separate corruption trial before Moro, who is expected to issue a verdict in late January or early February. If convicted, Lula could face more than 15 years in prison.

No dates have been set for the start of the other trials.

Lula is the biggest figure to be caught up in Brazil’s anti-corruption push, which began with the so-called “Car Wash” probe into Petrobras nearly three years ago.

The unprecedented investigation has led to charges against 200 people and 81 convictions. The charges involve at least 6.4 billion reais in bribes.

Lula’s former finance minister, Antonio Palocci, was also charged in the latest case, along with Marcelo Odebrecht, the former chief executive of Odebrecht.

The former CEO has turned state’s witness along with nearly 80 other executives from the firm. Their statements are expected to implicate more than 200 politicians.