This is the heart-stopping moment a two-year-old boy leaps onto metro train tracks in Milan, Italy.

The toddler's mother appears to panic and look for help after her son, Mohammed, suddenly falls onto the tracks.

An 18-year-old passer-by rushes to the boy's aid, lifting him to safety.

A station operator spotted the incident and halted the trains.

The operator and the rescuer, Lorenzo Pianazza, have been hailed as heroes.