Islam Times reports from Press TV: The protesters say that former US servicemen seeking medical support have admitted to dumping the toxic chemicals in South Korea's soil in 1978. The chemicals were the leftovers of those American forces used to kill and maim hundreds of thousands in Vietnam.
American sources have not confirmed discarding Agent Orange in the East Asian country.
South Koreans, however, suggest the US government is dragging its feet in investigating the case.
Following the demonstration, activists marched to Camp Carroll, the site of the alleged dumping, and demanded that the site be dug up.
Seoul said on Monday that it would examine the land that previously hosted American bases as the furor over the US forces' pollution of South Korea's environment widens.
Agent Orange is the code name for one of the herbicides and defoliants used by the US military as part of its herbicidal warfare program, Operation Ranch Hand, during the Vietnam War from 1961 to 1971.
Vietnam estimates that 400,000 people were killed or maimed, and 500,000 children born with birth defects as a result of the Agent Orange contamination.