Sao Paolo, Sep 11 (IANS/EFE): Brazilian President Dilma Rousseff and her main challenger in the upcoming elections, environmentalist Marina Silva, are virtually tied in voting intentions in both the first and second rounds, according to the latest opinion survey on the vote.

Released Wednesday, the results of the poll showed Rousseff garnering 36 percent of the vote in the Oct 5 contest, followed by Silva with 33 percent.

Social Democrat Aecio Neves would receive 15 percent of votes cast if elections were held today.

Other candidates trailed far behind, attracting just 4 percent each.

Last week, a Datafolha survey indicated that Rousseff had 35 percent support and Silva 34 percent, with Neves at 14 percent.

But if a second round should he held, then Silva is tipped to win with 47 percent to Rousseff's 43 percent.

Silva, a former environment minister, enjoyed a rise in support in the polls after formally replacing Brazilian Socialist Party candidate Eduardo Campos after he died in a plane crash.

The survey, carried out at the request of the newspaper Folha de Sao Paulo and the Globo communications group, was the largest yet in the present campaign, consulting 10,568 voters in 373 municipalities between Monday and Tuesday.