The Organization for the Prohibition of Chemical Weapons has marked the centennial of the first large-scale use of gas during World War I with a commemoration to pay tribute to all victims of such arms over the past century.

In a tribute close to the fields where Germany first used chlorine gas in its April 22, 1915 attack, OPCW Director General Ahmet Uzumcu said Tuesday that the purpose of his Nobel Peace Prize-winning organization could never be fully finished.

Uzumcu said that "our success cannot only be measured in weapons destroyed. It must extend to preventing new weapons from being developed and from being built."

The Allies and Germany used so many chemical shells during the 1914-1918 war that farmers are still ploughing them up to this day.