Attackers shot six vendors to death at an informal market Wednesday in the troubled Mexican resort city of Acapulco.

The killings took place around midday in a grocery store parking lot where the popular market is held.

Municipal government spokesman Jose Luis Mendez Rodriguez said the unknown gunmen exited a vehicle around midday and immediately opened fire, killing three men and three women.

The assailants fled into an adjacent neighborhood that has been the site of frequent armed clashes between gangs, and there were no immediate arrests.

Afterward, people wailed and hugged each other next to the blanket-shrouded bodies as police cordoned the area with yellow crime-scene tape.

One female victim lay face-down in a pool of blood, her head covered by a cardboard box. A woman wept as she cradled the head of a dead man.

There have been reports of threats and extortion demands at the market in the past, but never an attack like this one.

The grocery store is well away from Acapulco's tourist areas, along a northeastern boulevard that connects with the main highway in and out of the city.

Drug gang violence has turned Acapulco into one of the world's deadliest cities in recent years.

At least five people were killed in the city over the New Year's weekend, including three men whose severed heads were left on the roof of a car.