A week after the start of demonstrations that have witnessed the death of 19 people, the capital's Plaza Italia square on Friday overflowed as thousands more stood on neighbouring streets, reports Efe news.
The demonstration was set to start at 5 p.m. and within an hour, the crowd had swelled to more than a million, according to the municipal government.
Some in the rally held up a giant banner reading "Chile woke up," a phrase that has become the unofficial motto of the movement demanding the resignation of the country's President Sebastian Pinera.
The widespread unrest began on October 18 with a student protest in Santiago over a since-cancelled subway fare hike.
Protests escalated into violent incidents that have left 19 dead - some killed by police and soldiers deployed after the government declared a state of emergency, imposed curfews in several cities and put the military in charge of public order.
During the protests, Chileans also expressed their anger over low pensionsn, salaries and the high price of electricity, gas, university education and healthcare.
Chile's Congress, located in the central port city of Valparaiso, was evacuated earlier on Friday after demonstrators caused disturbances in the vicinity of the building.
The speaker of the lower house, Ivan Flores, ordered the suspension of the legislative session after a group of protesters gathered outside the building and unsuccessfully tried to force their way past members of the Carabineros, Chile's militarized national police.
According to the latest figures from the National Human Rights Institute (INDH), an autonomous public agency that monitors the actions of security forces, the number of arrests stands at 2,840.
The week-long protests have left 582 people injured, 295 of them struck by rubber bullets or tear-gas canisters.
A UN mission will travel to Chile next week to investigate possible human rights violations during the protests.
( With inputs from IANS )