Leftist to become Chile?s youngest ever president after beating far-right rival

A leftist former student leader has stormed to a resounding victory to become Chile's president-elect.

With nearly 97% of the vote already counted, Gabriel Boric claimed 55.8% to take a 12 percentage point lead over his far-right opponent, José Antonio Kast, an ultra-conservative father of nine, who quickly accepted his defeat and called Boric to congratulate him.

Boric declared to a vast crowd packed into a Santiago boulevard: "The times ahead will not be easy."

He paused only to lead the crowd in chants or smile up at the fireworks exploding overhead.

"Only with social cohesion, re-finding ourselves and sharing common ground will we be able to advance towards truly sustainable development - which reaches every Chilean," Boric said.

His relative inexperience was regularly highlighted by his rivals, but on Sunday night Boric was fluent and assured as he reiterated his campaign pledges before the raucous crowd of supporters.

He thanked each candidate in turn - including Kast - and reinforced his commitment to Chile's constitutional process, a key consideration for many as the country embarks upon this latest chapter in a turbulent period of transition.