Rio de Janeiro, October 22 (RHC-Mercopress) –- Brazilian President Dilma Rousseff is gaining momentum, but remains locked in a dead heat with challenger Aécio Neves ahead of Sunday's runoff to Brazil's presidential election, according to two surveys released on Monday.

The Datafolha poll shows the incumbent with 46 percent support, up three percentage points from the previous poll released on October 15th. Neves has 43 percent support, down two percentage points.

Centrist candidate Neves lost a slight but statistically insignificant lead over Rousseff for the first time since the first round of elections on October 5th, according to the survey by Datafolha polling firm.

Since then, the presidential race has turned increasingly ugly as the candidates scramble for undecided voters. They have swapped accusations of corruption and economic mismanagement in heated televised debates over the past few days in what is shaping up to be Brazil's tightest election in decades.

A survey by polling firm MDA released earlier on Monday showed Rousseff with 45.5 per cent of voter support versus 44.5 per cent for Neves. The difference between the two remains within the margin of error of both polls.

Excluding undecided voters, spoiled and blank survey responses, the Datafolha poll showed Rousseff had 52 percent against 48 percent for Neves, a senator and former state governor.