"The ruling recognises responsibility lies with the defendants, who were manufacturers of defoliants, for damages suffered by South Korea's veterans to the Vietnam War due to a product defect," the court said in a summary.

The ruling awarded damages ranging from 6 million won to 46 million won to the former veterans who brought the case in two class-action suits.

The defoliant Agent Orange was dumped by US warplanes on Vietnamese forests between 1962 and 1971 to destroy sources of food and cover.

Among the chemical by-products of Agent Orange is dioxin, a compound that can cause cancer, deformities and organ dysfunction.

The chemical companies argued in US cases they produced Agent Orange according to US government specifications and that there has never been a proven connection between the agent and the health problems it is accused of causing.

In 1984, seven chemical companies, including Dow and Monsanto, agreed to settle out of court for $180 million with US veterans who claimed Agent Orange caused cancer and other health problems.

More than 300,000 South Korean troops fought in the Vietnam with US-led forces, historians said.

Due to problems arising from jurisdiction and the amount of time that has elapsed since the war, legal experts said it will be cumbersome or perhaps impossible for the veterans to collect damages, South Korean media reported.