Chile's Centre-left leader Michelle Bachelet has held a big lead in the presidential election, but fell short of the 50 percent of votes necessary needed to avoid a December 15 runoff, according to partial results.

Bachelet, who led Chile between 2006 and 2010 as its first female president, had 46.7 percent support with 78 percent of votes counted on Sunday night.

Her second-place rival, Evelyn Matthei, the candidate for the right-wing governing coalition, had 25.2 per cent of the votes, while seven other candidates trailed far behind.

Voters also were choosing all 120 members of the chamber of deputies, 20
senators and local and regional officials. The legislative vote will be key to whether Bachelet's ambitious social-minded reform plans will succeed. Results from congressional elections were expected later on Sunday.

Bachelet, 62, has promised to narrow the worst income inequality among the 34 member states of the Organization for Economic Co-Operation and Development (OECD) by leveling the playing field in education.

She has also pledged to rewrite a constitution that dates back to Augusto Pinochet's 17-year dictatorship, during which she was briefly a political prisoner. Her father, an Air Force Brigadier-General, was tortured and killed by Pinochet's regime.

Bachelet's centre-left Nueva Mayoria [New Majority] coalition, which spans the political spectrum from communists to moderate Christian Democrats, must also win big in congressional elections on Sunday in order to muster the political might needed to implement those changes.

"In order to confront inequality, I invite you to vote en masse for the Nueva Mayoria this Sunday. We want to win in the first round because we have a lot of work to do," Bachelet told a packed crowd at her campaign's closing ceremony on Thursday.

A candidate winning over half the votes would be elected outright - something that has not happened in 20 years.

Bachelet was constitutionally barred from seeking immediate re-election after her first term, but left office enjoying stratospheric popularity.

The Andean country moved to a voluntary voting system from a compulsory one last year, creating a degree of uncertainty in electoral forecasts.

Source: Al Jazeera and agencies