The United Nations nuclear agency has endorsed a plan to help strengthen global nuclear safety in the wake of Japan's Fukushima accident six months ago.

The International Atomic Energy Agency approved the plan Thursday at its annual conference in Vienna , despite complaints from some members that the plan does not go far enough. The disaster spurred a worldwide re-examination of the use of nuclear energy and a call for new measures to avoid such accidents in the future.

The voluntary plan, prepared by the office of IAEA Director General Yukiya Amano, calls on member states to promptly assess their nuclear power plants to determine whether they can withstand extreme natural hazards. The members would also take steps to remedy any weaknesses and strengthen emergency preparedness.

The plan was passed by the IAEA's 35-nation governing board last week. But the debate underlined disagreements among nations seeking mandatory commitments and those wanting to keep outside safety inspections of their nuclear installations voluntary, stressing the responsibility of national authorities.

The Fukushima accident occurred after a powerful earthquake and a massive tsunami struck Japan on March 11, causing the reactor fuel rods at the plant to begin melting down as power and cooling functions failed. The quake and tsunami left more than 20,000 people dead or missing, forced the evacuation of 80,000 people and left tens of thousands homeless.