A landmark treaty to ban some forms of cluster bomb has been signed by more than 100 nations in Oslo.

Norway, which played a key role in hammering out the worldwide ban on using, producing, transferring and stockpiling cluster munitions, was the first country to sign the Convention on Cluster Munitions (CCM) on Wednesday.

Jonas Gahr Stoere, the Norwegian foreign minister, said: "This is a historic day when a majority of states are committing to ban cluster munitions, making a new international norm that will make a considerable difference for thousands and thousands of people all over the world."

Nations at the conference also called on major arms producers such as China, Russia and the United States to join them in signing the treaty.

Between 1964 and 1973, the US air force dropped 260m cluster bombs on Laos, or the equivalent of a fully-loaded B-52 bomber's payload dropped every eight minutes for nine years.