According to the Saudi civil defence directorate, the crowd became dangerously congested at the intersection of two streets, known as 204 and 223, as the faithful were making way towards the Jamarat Bridge, which overlooks the stone columns where pebbles are cast.
The bridge's purpose is specifically to ease the pressure of the crowds, which can reach three million during the busiest times of year.
Ambulance sirens blared as rescue crews rushed the injured to nearby hospitals, while more than 220 rescue vehicles and some 4,000 members of the emergency services were deployed to provide alternative exit routes.
Amateur video shared on social media showed corpses lying amid crushed wheelchairs used by some disabled pilgrims.
The tragedy comes despite the Saudi authorities installing sophisticated crowd analytics software which is linked to central control room where officials can analyse and predict where pinch-points and surges are likely to take place.