Four of those killed died at the scene and the remaining three died while receiving treatment for their injuries, local police said. Five more people were seriously injured when the gunmen stormed the bar.
No one has yet been arrested on suspicion of the shooting, which occurred on Saturday morning local time.
Criminal gangs that smuggle stolen fuel are active in the central Mexican state of Hidalgo, to which the city of Tula belongs, but mass shootings like the one on Saturday are unusual.
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