With 11 games left, the champions stay seven points clear of second-placed Juventus, who beat city rivals Torino 1-0 thanks to Giorgio Chiellini's 81st minute header from a Pavel Nedved free kick.
Torino goalkeeper Matteo Sereni had tried his best to extend his side's seven-game unbeaten run when he made a full length save on the line to stop Vincenzo Iaquinta's first-half header.
Juve coach Claudio Ranieri left Alessandro Del Piero and some other first teamers on the bench with one eye on Tuesday's Champions League second leg match with Chelsea.
Inter boss Jose Mourinho played almost his strongest side but centre backs Marco Materazzi and Nicolas Burdisso went off injured in the first half and look doubtful for the Champions League clash at Manchester United on Wednesday.
Defenders Cristian Chivu and Walter Samuel were already struggling to be fit for the last 16 game against the holders and coach Mourinho now has a real headache.
WEAK SHOT
He was forced to push midfielder Esteban Cambiasso back into central defence against fifth-placed Genoa and as usual the Argentine put in a committed performance alongside goalkeeper Julio Cesar, who made several smart saves.
"We have been able to control them well and it was a fair result," Cambiasso told Sky television. "We hope some of our team mates recover."
Ibrahimovic, rested for Wednesday's 3-0 Italian Cup semi-final first-leg defeat by Sampdoria on the same ground, opened the scoring after two minutes when he raced onto Dejan Stankovic's pass and lifted the ball over keeper Rubinho.
Balotelli, accused of diving to win a penalty in last weekend's 3-3 draw with AS Roma, was at the centre of more controversy after 61 minutes when his weak shot was adjudged to have crossed the line despite Marco Rossi's attempts to clear.
Sixth-placed AS Roma, who host Arsenal in the Champions League on Wednesday, earlier lost David Pizarro to injury and had fellow midfielder Daniele De Rossi sent off in a 1-1 home draw with Udinese.
Felipe put Udinese ahead in the 54th minute after a mistake by Roma keeper Doni but substitute Mirko Vucinic equalised with a strong finish before De Rossi was dismissed for dissent.
AC Milan, in third, host Atalanta on Sunday.
