Fifteen people were injured, some in the stampede, after at least one shooter opened fire before dawn at the Blue Parrot nightclub during the BPM festival, Mayor Cristina Torres told Turquesa radio.
Three of the dead are foreigners, said Torres, mayor of the municipality of Solidaridad, which includes the popular beach resort.
"For the moment we have indications that one person opened fire," Torres said, adding that authorities were contacting the US, Canadian and Colombian consulates to provide information about their citizens' conditions.
She said the shooting appeared to have taken place inside the club, causing people to flee in panic.
Playa del Carmen is 68 kilometers (42 miles) south of Cancun. The region, popular among American and European tourists, has been largely spared from the drug violence plaguing other parts of Mexico.
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