An international treaty on cluster bombs has come into force, banning the use, production and storage of the weapons.
The weapons scatter small explosives over a wide area.
The convention has been adopted by 108 countries and ratified by 38, the BBC reports.
The US, Russia, China and Israel are among those that have rejected the convention.
Pope Benedict has joined campaigners to call on all countries to sign up to the ban.
The International Committee of the Red Cross says the treaty will stigmatise the use of the munitions.