Cluster bombs have been used in Cambodia, Lebanon and Kosovo
An international treaty banning cluster bombs will enter into force in August after it was ratified by a 30th country, the UN says.
Burkina Faso and Moldova became the latest states to ratify the treaty.
The convention bans the production and use of cluster munitions and obliges states to compensate victims.
First developed during World War II, cluster bombs contain a number of smaller bomblets designed to cover a large area and deter an advancing army.
But campaigners, including some in the military, have long argued they are outmoded and immoral because of the dangers posed to civilians from bombs that do not explode and litter the ground like landmines.
The treaty is binding only on countries that have signed and ratified it.
Since the convention was opened for signature in Oslo in 2008, 104 countries have signed on but only 30 have ratified, according to the Cluster Munition Coalition (CMC), which represents 200 activist groups against cluster bombs.
Some of the biggest stockpilers - including the US, Russia, China and Israel - are not among the signatories.
Some major European states - including France, Germany and Spain - have ratified the convention. The UK and Italy have signed, but not ratified.
UN Secretary-General Ban Ki-moon called the 30 ratifications a "major advance on the global disarmament agenda" and said the treaty's entry into force "demonstrates the world's collective revulsion at the impact of these terrible weapons".
The CMC said the first meeting of states that have ratified the convention would be held in November in Laos, the country most heavily contaminated by cluster munitions as a result of US bombing more than 30 years ago.
Steve Goose, the coalition's co-chair and director of the arms division at Human Rights Watch, called on all countries to join the convention before November.
"Cluster munitions are already stigmatised to the point that no nation should ever use them again, even those who have not yet joined the convention," Mr Goose said in a statement.
HOW A CLUSTER BOMB WORKS
1. The cluster bomb, in this case a CBU-87, is dropped from a plane and can fly about nine miles before releasing its load of about 200 bomblets.
2. The canister starts to spin and opens at an altitude between 1,000m and 100m, spraying the bomblets across a wide area.
3. Each bomblet is the size of a soft drink can and contains hundreds of metal pieces. When it explodes, it can cause deadly injuries up to 25m away.