Organizers estimated that the number of participants in the Saturday rally, the third since the scandal came into focus last month, topped 1 million in Seoul alone, according to local media reports. Last Saturday, some 200,000 people turned out in the capital city.
It would be the country's largest mass rally at least since June 1987 when about 1 million demonstrators gathered to ouster the military dictatorship. In 2008, some 700,000 protested against then-President Lee Myung-bak who resumed US beef imports during the outbreak of mad cow disease.
Police said around 260,000 people turned out in Seoul, beating its earlier expectation of up to 170,000.
Ranging from couples with their babies and children to students in school uniforms and grey-haired old men, ordinary South Koreans crowded the Seoul streets.