MEXICO CITY, Nov 1 (Reuters) - Mercedes' Kimi Antonelli became Formula One's youngest world champion at 20 years old on Sunday in a red-flagged and restarted Mexico City Grand Prix won by Red Bull's Max Verstappen.

The first Italian champion since 1953 finished third, sobbing with joy over the team radio as he took the chequered flag at the high-altitude Autodromo Hermanos Rodriguez, with his overall lead now an unassailable 119 points.

Ferrari's Lewis Hamilton started from pole position and took a close second place on an afternoon of drama with two safety cars, multiple crashes and an agonising 33-minute halt with 25 of the 71 laps remaining.