RIO DE JANEIRO -- Brazilian police pulled former President Luiz Inacio Lula da Silva in for questioning on Friday and searched properties connected to the leader and his family, drawing the country's most towering political figure closer into the sprawling corruption case centred on the oil giant Petrobras.

Police turned up early Friday at addresses belonging to Silva, including his residence near Sao Paulo and the Instituto Lula, his non-profit organization.

Acting on a summons, police took Silva to the federal police station at Sao Paulo's Congonhas airport, where he was questioned for about four hours and released.

Silva reacted with indignation, saying the Petrobras corruption case has become a political witch hunt targeting him and his governing Workers' Party.

Silva, referring to himself by his nickname, suggested that the country's elite is out to "criminalize the Workers' Party, criminalize Lula (since) they could want to continue in power."

He said the action had fortified his desire to seek the presidency again in 2018, though he said he had not yet decided to run.

Silva said he already answered investigators' questions on three occasions and would have done so again without a police escort, if asked.

"I felt like a prisoner this morning," he said. "I think I deserved more respect than that."

Officials said they were looking into 30 million Brazilian reais ($8.12 million) in payments for speeches and donations to the Instituto Lula by construction firms that have been crucial players in the Petrobras corruption scheme. They were also looking into whether renovations and other work at a country house and beachfront apartment used by Silva and his family constituted favours in exchange for political benefit.

"No one is exempt from investigation in this country," said public prosecutor Carlos Fernando dos Santos Lima. "Anyone in Brazil is subject to be investigated when there are indications of a crime."

Speaking to GloboNews television network, federal police official Igor Romario de Paula said the session "was calm," adding that Silva "answered the questions that were posed him."

In response to the day's events, Silva's attorneys asked the Supreme Court to suspend the investigation against the former leader, but the court has yet to rule on the matter.

In a statement, the Lula Institute said "nothing justified" the morning's events. It insisted that "Lula never hid patrimony or received undue advantages either before, during or after governing the country."

Clashes broke out between Silva's supporters and detractors outside the ex-president's apartment in Sao Bernardo do Campo and at Congonhas airport, with several hundred Workers' Party supporters chanting pro-Silva slogans.

Lima said the decision to take Silva in for questioning was made for security reasons, to avoid demonstrations and other obstructions.

Silva, a plainspoken former union leader, was among the most revered leaders in Brazilian history when he left office in 2010, leaving the post in the hands of his chosen successor, Rousseff. He has made no secret of his continued presidential aspirations, saying he was mulling a run for the office in 2018.

Silva's party called for sympathizers to take to the streets in support of Silva and its president Rui Falcao issued a video statement calling the detention "a political spectacle" that revealed the "true character" of the probe known as Operation Car Wash.

"It's not about combatting corruption but simply to hit the Workers' Party, President Lula and the government of President Dilma," Falcao said.

On Twitter, Aecio Neves, the opposition presidential candidate who narrowly lost to Rousseff in the 2014 race, said "the advance of Operation Car Wash is a definitive step toward Brazilians knowing the truth."

The summons of Silva brings the sprawling probe closer to Rousseff, though the once-close allies have visibly distanced themselves in recent months.

While Rousseff herself has not been accused of wrongdoing in the Petrobras probe, she is facing impeachment proceedings in Congress for her government's alleged use of the country's pension fund to shore up budget gaps. Rousseff denies the allegations.

Legal analysts said that the fact Silva was brought in for questioning suggested any possible case against him was still in its early phases.

"Police are still collecting evidence. There is no smoking gun because if there were, the searches wouldn't be needed," said Jair Jaloreto, a Sao Paulo-based expert on money laundering.

The Petrobras scandal has already ensnared top businessmen and heavyweight politicians. On Thursday, the Supreme Court allowed corruption charges in the case to be brought against Eduardo Cunha, a top opposition figure and speaker of the lower house of Congress.

Prosecutors say more than $2 billion was paid in bribes by businessmen to obtain Petrobras contracts. Investigators also have said that some of the money made its way to several political parties, including the Workers' Party.

A lathe operator at a metal factory who entered politics as a labour union leader, Silva was widely seen as representing the common man, and his ascension to the country's highest office was hailed in a country where politics have long been dominated by the elite. During his two terms in office, from 2003-2010, Silva presided over galloping economic growth that pulled tens of millions of poor Brazilians into the ranks of the middle class.

Despite a votes-for-bribes scandal that took down his chief-of-staff, Silva left office with record high popularity levels and his hand-picked successor, Rousseff, handily won the presidency.

Both have lost popularity as Brazil slipped into its worst recession in decades and the Car Wash investigation spread. Rousseff saw her approval ratings dip into single digits, though they've rebounded slightly of late. Silva's ratings have also slid since allegations against him emerged in the press.

Associated Press writer Stan Lehman contributed from Sao Paulo