A global treaty banning cluster munitions has gone into force.
The Convention on Cluster Munitions, which became binding international law on Sunday, prohibits the use, production and stockpiling of the weapon, which is blamed for killing and maiming tens of thousands of civilians.
Thomas Nash, from the Cluster Munition Coalition, a network of 200 civil society organisations, hailed the ban.
"This is the most significant piece of international humanitarian law to enter into force since the land mine ban 10 years ago. From this moment on, countries have a legal obligation to assist the victims," the Reuters news agency quoted him as saying.
The treaty requires signatories to destroy stockpiled cluster munitions within eight years, clear contaminated areas within 10 years and help affected communities and survivors.
The Convention on Cluster Bombs was first adopted in May 2008 and ratified by 37 states including Britain, France, Germany and Japan, which all have significant stocks.
Cluster bombs are dropped from planes or fired by mortars before the canisters open mid-air, releasing bomblets that scatter over a wide area. Most explode immediately, but those that fail to detonate on impact can claim victims many years after the end of the conflict.
More than two dozen countries have been affected by cluster bombs and activists say three out of five casualties occur during day-to-day activities.
Most of the victims are children and some are killed when they mistake the bomblets for toys.
The United Nations estimates almost half of all casualties are from Laos, where people are still at risk of being injured from unexploded bomblets.
Between 1964 and 1973, at the height of Vietnam War, the US military dropped more than 2 million tons of explosive ordnance, including an estimated 260 million cluster munitions, mainly to disrupt enemy supply lines that passed through Laos.
It is thought that around 30 per cent of bomblets failed to explode on impact, and over two-thirds of the country is still contaminated. Experts say they kill or injure about 300 people a year.
Countries that have signed the treaty into law include the UK, France, Germany and Japan, all of which have significant stocks of the weapon.
But the Cluster Munition Coalition said it needs to persuade more states to sign.
The United States, the world's largest producer with the biggest stockpile of 800 million submunitions, has refused to sign the treaty so far, although it says it will ban the weapon from 2018.
China, Russia and Israel have also stayed away and do not disclose their stocks.
Lou Maresca from the International Committee of the Red Cross told Al Jazeera: "We've often seen that the establishment of a new international humanitarian law treaty can nevertheless impact on states which are not a party to it.
"We've already seen that the existence of this treaty has helped change the practice and provoke a re-evaluation of the role of cluster munitions even in major military powers."