The head of the United Nations nuclear watchdog agency is urging the world to re-examine safety measures in the aftermath of the accident at Japan's Fukushima Daiichi nuclear facility three months ago.

Yukiya Amano said adherence to current practices is “not an option.” His remarks came at the start of a week-long meeting of the International Atomic Energy Agency in Vienna Monday.

Amano said nuclear safety will remain a national responsibility, but he said U.N. experts should be allowed to carry out random safety reviews of nuclear power plants.

There are no mandatory, international nuclear safety regulations — only IAEA recommendations that national regulators are in charge of enforcing. Amano called for strengthening IAEA standards and ensuring they are applied.

The International Atomic Energy Agency is set to issue a report criticizing Japan's handling of the nuclear crisis at the Fukushima Daiichi power plant. That review — based on a fact-finding mission to Fukushima — says Japanese officials failed to anticipate threats to nuclear facilities from earthquakes and tsunamis.

It also says nearby residents were not evacuated according to IAEA standards following the crisis sparked by the quake and tsunami in March.