City government spokesman Jose Luis Mendez Rodriguez says the killings took place yesterday in a grocery store parking lot where the popular market is held.
Rodriguez says the unknown attackers exited a vehicle around midday and immediately began shooting. Three men and three women were killed.
The attackers fled into an adjacent neighbourhood that has been the site of frequent armed clashes between gangs. There were no immediate arrests.
The grocery store is well away from Acapulco's tourist areas, along a northeastern boulevard that connects with the main highway out of the city.