Chileans have headed to the polls for a second referendum aimed at replacing the country's dictatorship-era constitution, with voters asked to approve or reject a more conservative draft.

Voting started on Sunday at 1100 GMT and is expected to close at 2100 GMT, with results due a few hours later.

The latest version was overseen by the far-right opposition Republican Party after voters roundly rejected a progressive draft in September 2022 that attempted to enshrine environmental protections and the right to elective abortion.

Leftist President Gabriel Boric said last month that it would be his last attempt to reform the constitution in order to focus on stability and long-term development.

Polls, banned in the two-week run-up to the referendum, have predicted another rejection.

The process to rewrite the 1980 constitution, adopted under the Augusto Pinochet military dictatorship, began as a bid to ease mass protests that broke out in October 2019 against social inequality.

In a 2020 referendum, 80 percent voted for replacing the constitution.

However, four years after the protests erupted, enthusiasm has been dampened by the pandemic, inflation and economic stagnation, a growing sense of insecurity, and voter fatigue, say analysts.

Boric's approval plummets

The opposition has presented the vote as a referendum on Boric, who rode the wave of public discontent to be elected Chile's youngest ever leader in late 2021 at 35.

Boric, whose approval has plummeted to around 30 percent, already suffered a setback in May when Chile's far right Republican Party came in first in a nationwide vote to choose the members of the rewrite committee.

The 1980 constitution is widely blamed for allowing companies and the elite to enrich themselves at the expense of the poor, working classes.

The first rewrite included stronger protections for Indigenous rights, proposals to protect natural resources such as water, and required women to hold at least half of positions in public institutions.

The currently proposed constitution does for the first time recognise Indigenous peoples, which make up 12 percent of the population, but does not respond to their request for greater autonomy.

Heiss said the latest rewrite "falls between the 1980 constitution and one even more to the right," especially on issues like abortion and public safety.

The new version aims at enshrining the right to life from conception, which experts believe could lead to a challenge of existing laws.

The new draft also allows for the expulsion in "the shortest possible time" of undocumented immigrants, with the right blaming rising crime on an influx of Venezuelans fleeing economic crisis in their country.