Fluminense regained the lead they had lost to Corinthians last week with a 2-1 victory away to Vitoria, while Libertadores Cup winners Inter climbed into the top four in fourth place.
Flu have 48 points after 25 matches, one point more than Corinthians. Third-placed Cruzeiro, four points off the pace, were beaten 4-1 at Santos on Saturday.
Inter have 41 points, having leapfrogged Botafogo who dropped out of the top four after a 1-1 draw at home to Atletico Paranaense.
In a dramatic finish to an exciting match at the Beira-Rio in the southern city of Porto Alegre, Inter conceded a penalty one minute into added time and had right back Nei sent off for handball.
Midfielder Bruno Cesar put Corinthians level at 2-2 from the spot only for Andrezinho to score the winner two minutes later in the last move of the match. Central defender Paulo Andre was shown the red card for a foul and from the free-kick Andrezinho pounced on the rebound after it came back off the wall.
Tinga had given Inter a 1-0 lead on the half hour, Jorge Henrique equalised in the 64th minute and Alecsandro put the home side ahead again in the 76th.
Fluminense, who had led the standings from July until their defeat by Corinthians last week, beat Vitoria in the northern coastal city of Salvador with all three goals coming in a six-minute spell.
They went ahead with a 58th-minute penalty from their Argentine captain Dario Conca, Henrique equalised in the 62nd and striker Rodriguinho hit the winner less than two minutes later.
"The championship is very treacherous. We've won two important matches this week, but I'm not getting carried away. I'm going to push the boys harder," Fluminense coach Muricy Ramalho told reporters.
"We've lost the lead but the championship hasn't ended yet. Don't forget we have a game in hand," said Corinthians coach Adilson Batista.
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