A year after the start of a mass wave of social unrest, Chileans vote Sunday in a referendum to change a dictatorship-era constitution seen as the bedrock of the nation's glaring inequalities.

An unusually heavy police presence on Friday kept protesters away from gathering en masse on Santiago's Plaza Italia, the epicenter of the protests, as they sought a final chance to voice their demands before Sunday's historic vote.

Police fired arcs of pressurized water from armored vehicles to push stone-throwing demonstrators back from the area.

Security was tight in the capital ahead of a 11 pm - 5.00 am curfew, after violence marred last Sunday's largely peaceful march to mark the anniversary of the start of the protests, and two Catholic churches were set ablaze.

A woman with a face mask reading 'Yes, I do approve the new constitution' takes part in a rally in support of amending the charter established under the military rule of General Augusto Pinochet
A woman with a face mask reading 'Yes, I do approve the new constitution' takes part in a rally in support of amending the charter established under the military rule of General Augusto Pinochet AFP / Martin BERNETTI

The country's conservative billionaire president Sebastian Pinera, who has remained neutral in the campaign, has called on Chileans to vote in numbers in the historic plebiscite, and to reject violence.

The referendum was a key requirement from protesters during months of social unrest unseen since the South American country's return to democracy in 1990.

Chileans will be asked two questions on Sunday; to approve or reject a new constitution, and if so, what kind of body should draft it -- a mixed assembly composed equally of lawmakers and citizens, or a 155-member convention made up entirely of citizens.

Opinion polls show more than 70 percent support a new constitution, with just 17 percent voting for rejection. Polls also indicate 70 percent will back a constituent all-citizen convention, to be elected in April 2021.

The final draft of the constitution would be put to the public in a referendum in 2022.

People rally in Santiago in support of amending Chile's constitution ahead of Sunday's referendum
People rally in Santiago in support of amending Chile's constitution ahead of Sunday's referendum AFP / Martin BERNETTI

The country's pre-referendum nerves had moments of humor.

Voters must bring their own pencils and gel to polling stations on Sunday because of the coronavirus pandemic. A stall in the city center was selling blue pencils at a preferential rate for some: A sign for identical pencils read "Approve: 250 pesos" and "Reject: 9,999 pesos".

For those supporting change, mainly the leftist opposition parties, a new charter would allow a fairer social order to replace the persistent inequalities of the constitution forged under the 1973-1990 rule of Augusto Pinochet.

Opinion polls show more than 70 percent support a new constitution, with just 17 percent saying no
Opinion polls show more than 70 percent support a new constitution, with just 17 percent saying no AFP / Martin BERNETTI

"One way or another changes are coming and it would be better to feel it was thanks to a new constitution that we all participated in -- and not a constitution created by a small group during a dictatorship so that another small group would stay in power forever," said Alejandra Pizarro, a 23-year-old student at an "Approve" rally outside the presidential palace late Thursday.

The new constitution would expand the role of the state in providing a welfare safety net, and in the process add further pressure on an economy struggling to emerge from the Covid-19 health crisis.

Some conservatives reject the proposed change, saying the constitution has been key to Chile's decades of economic growth and stability.

"I don't want my country to fall into the same hands that Argentina, Venezuela and a lot of other disastrous countries have," said Hernan Allende, 63, a property broker at a "Reject" rally.

President Sebastian Pinera caved in to protesters when he agreed on a constitutional referendum in November after three weeks of protests, he said.

"That's where this whole disaster comes from, he hasn't had a strong enough hand to stop crime and terrorism," Allende said, alluding to rioters who have regularly faced off against the police.

Just over a year ago, when Harvard-educated billionaire Pinera vaunted Chile as a progressive "oasis" in a Latin America convulsed by unrest, little could he know that within 10 days his country would ignite in flames.

The billionaire conservative made a speech in early October holding his copper-rich country up as a symbol of regional stability, but then a student protest against a hike in public transport fares lit the fuse on a tinderbox of long-festering inequality.

It began on October 18 as a protest in the Santiago metro, but protesters' grievances in massive anti-government protests quickly expanded to include demands for better health, pensions, salaries and education.

Some 30 people died, most in street clashes with militarized Carabineros forces in the resulting months of turmoil, and thousands were wounded.

A year later, protesters have yet to be assuaged by reforms, but voters are expected to embrace a chance to throw out Pinochet-era laws that concentrated economic power in the hands of a core of Chile's wealthiest families.