Some 139 million Brazilians were called upon to elect 5,561 mayors and 48,000 municipal councilors for four-year terms among 450,000 candidates representing more than 20 political parties.

In Sao Paulo, the exit polls released by the televison channel Globo after the nationwide balloting closed, showed that opposition Brazilian Social Democratic Party (PSDB) candidate Jose Serra will face off against his ruling Workers Party (PT) rival Fernando Haddad in a runoff vote scheduled for October 28.

The exit polls gave Serra, a former presidential candidate, 30 percent of the vote, against 29 percent for Haddad, who got the active support of ex-president and PT founder Luiz Inacio Lula da Silva.

Russomanno, a populist ex-consumer advocate backed by a powerful evangelical Christian church, finished third with 23 percent.

He had led throughout the campaign although his rivals closed the gap in the past few days.

Some analysts had suggested that Haddad would be hurt by the ongoing corruption trial embroiling Lula's PT.

Thirty-seven former ministers, lawmakers, businessmen and bankers are facing prosecution before the Supreme Court over the alleged scheme that ran from 2002 to 2005 during Lula's first term.

While Lula was cleared, the scandal nearly cost the 66-year-old his re-election in 2006.

In the other major race in Rio, Paes, a PT-backed member of the centrist PMDB, won re-election with 69 percent of the vote and will thus remain at the city's helm during the 2016 summer Olympics.

The mandatory electronic voting began at 1100 GMT and polling stations closed at 2000 GMT.