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Toulouse nearly found an instant response just two minutes later, but Clement Chantome's strike flew just wide of the target.
However, Rennes doubled their lead 10 minutes before the break when Ahamada missed a punch up against Jean II Makoun from a Alessandrini cross, and Bakayoko was on hand to nod the ball into an open goal from all of a yard out.
Rennes put the game to bed just before half time, when Kadir slammed a free kick from the left edge of the box which took a deflection on its way to flying into the back of the net.
The visitors nearly found a fourth instantly following the restart, but Oliveira's shot was narrowly off target.
However, Oliveira did get on the scoresheet with 26 minutes remaining as his half-volley crept through a crowd of bodies from close range.
Oliveira then compounded Toulouse's misery further by adding a fifth goal in the final 10 minutes of the match.
Rennes climb to eighth in Ligue 1 while Toulouse sink to 12th.