Brazil's Brandao, Argentine Lucho Gonzalez, Senegal's Mamadou Niang and Frenchmen Benoit Cheyrou and Mathieu Valbuena scored for Marseille, giving the team their most emphatic home victory of the season.
The result lifted Marseille to 39 points, just one adrift of fourth-placed Olympique Lyon, but with a game in hand.
Lyon were reduced to 10 men in their match against Toulouse after Jean Makoun was sent off in the 68th minute for a second yellow card, but they managed to secure a point with a 0-0 draw.
Saint-Etienne, meanwhile, ended Monaco's four-game winning streak with a decisive 3-0 home win on Sunday.
Sixth-placed Monaco, unbeaten in Ligue 1 since December 16, had no answer to the pressure from Saint Etienne, who had not won at home in the championship since October.
Goals by Blaise Matuidi in the 13th minute, Argentine striker Gonzalo Ruben Bergessio a quarter of an hour from the end and Emmanuel Riviere just before the finish lifted St Etienne to 16th place in the table.
At the end of the 23rd round, Girondins Bordeaux still lead the Ligue with 48 points despite their 4-2 loss to Stade Rennes on Saturday, three points ahead of Montpellier who cut the gap at the top with their 2-0 victory over Boulogne-sur-Mer.
