Stricter UN rules on preventing nuclear materials from falling into the hands of terrorists will come into effect in May, the International Atomic Energy Agency (IAEA) announced Friday in Vienna.
So far, the Convention on the Physical Protection of Nuclear Material was aimed at making sure that uranium or plutionium does not become accessible to violent extremists during transportation from one country to another.
The amended version of the pact obliges governments to also protect nuclear installations and materials within countries.
The advances of Islamic State extremists in the Syrian war and recent attacks in Europe have heightened international concerns that terrorists could try to obtain radioactive materials or attack nuclear power plants.
The updated convention broadens the list of punishable criminal acts, by including smuggling of nuclear materials, sabotaging nuclear installations and creating environmental hazards.
Once the amendment comes into effect on May 8, countries will also have to share intelligence information if they learn of nuclear terrorist plots being planned in other countries.
The amendment "will help reduce the risk of a terrorist attack involving nuclear material, which could have catastrophic consequences," IAEA chief Yukiya Amano said.
However, the new version does not contain a mechanism to make sure that all countries honour their obligations.
After Nicaragua signed on to the tougher rules on Friday, the necessary threshold of 102 countries that back the amendment was reached, triggering its entry into force in a month's time.
North Korea and Iran are among the few nuclear countries that have neither adopted the original 1987 convention nor the updated version.