Protests that flared up in October -- initially over a rise in metro fares -- abated during the summer holidays before breaking out anew in recent weeks, raising authorities' concerns over mass gatherings.

Ricky Martin, Maroon 5 and Puerto Rican star Ozuna are the headline acts as the annual festival in the Pacific Coast resort city begins amid threats of protests.

Calls to disrupt the festival have circulated on social networks, with protests to center on the Quinta Vergara  amphitheater where the festival has been held for more than six decades. 

Organizers have installed metal detectors at entrances and brought festival opening times forward for the duration of the six-day festival. 

In another sign of official nervousness, the festival's traditional Hollywood-style red carpet opening, one of Chile's most watched televised events, has been canceled.

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Ricky Martin's message

Ricky Martin, who supported the social protests, will open the festival on Sunday with a performance from his Movimento Tour.

At the height of the protests, Martin addressed a message to Chile's President Sebastian Pinera on social media: "You have to know that the will of a people is respected, is obeyed, is fulfilled. Listen to your people."

Outspoken Chilean star Mon Laferte's performance will be closely watched. She bared her breasts in a message of support for protesters at the Latin Grammy Awards in Las Vegas in November.

Stand-up comedians have been warned to refrain from making jibes at the authorities during the festival, which runs through February 28.

Since authorities announced a modest hike in metro fares in the capital Santiago on October 18, more than 30 people have died in protests.

They quickly mushroomed into wider discontent over inequality and the rejection of conservative billionaire Pinera and his government.

A nationwide referendum on  changing the dictatorship-era constitution is set for April.