The court in the Paris suburb of Evry ruled that it did not have the jurisdiction to judge a case involving the wartime actions of the U.S. government, the ruling seen by AFP said.

Tran To Nga, a former journalist born in 1942 in what was then French Indochina, accused the chemicals firms, including Monsanto and Dow Chemical, of causing grievous harm to her and others by selling Agent Orange to the U.S. government, which used it to devastating effect in the war.

She also accused them of causing damage to the environment.

Dismissing the case the court said that the companies were acting "on the orders" of the U.S. government, which was engaged in a "sovereign act."

NGOs estimate that four million people in Vietnam, Laos and Cambodia were exposed to the 76 million liters (20 million gallons) of Agent Orange sprayed by U.S. forces to destroy ground cover and food sources in its battle with North Vietnamese troops between 1962 and 1971.

Tran To Nga suffers from typical Agent Orange effects, including type 2 diabetes and an extremely rare insulin allergy.

One of her daughters died of a malformation of the heart.

The multinationals have argued that they could not be held responsible for the use the American military made of their product.