Vienna - The situation at Japan's earthquake-damaged nuclear power plant is "very serious", Yukiya Amano, Director General of the International Atomic Energy Agency (IAEA), said.
He expressed his wish to fly personally to Japan to assess the situation and talk to high-level Japanese officials. An IAEA expert team will also be sent to Japan as soon as possible.
An earlier IAEA statement said Japanese officials voiced concerns about the condition of the spent nuclear fuel pool of Unit 3 and Unit 4 at Fukushima No.1 nuclear power plant.
Japanese Defence Minister Toshimi Kitazawa announced Wednesday that Special Defence Forces helicopters planned to drop water onto Unit 3, and officials were also preparing to spray water into Unit 4 from ground positions, and possibly later into Unit 3.
Some debris on the ground from the 14 March explosion at Unit 3 may need to be removed before the spraying can begin.
Meanwhile, other countries have begun to review the safety of their nuclear reactors.
The European Union's energy chief Guenther Oettinger said the EU would conduct "stress tests" on its member states' nuclear power plants. The tests would include risk assessments of possible damage by earthquakes and high water levels.
The EU tests would be concluded by the end of the year, Oettinger said, adding that thorough stress tests would also take place in nuclear plants of neighbouring countries, including Turkey, Russia and Switzerland.
Europe now has about 143 nuclear power plants in 14 countries.
German Chancellor Angela Merkel said the country would shut down seven of its oldest nuclear reactors built before 1980 for three months for a safety probe.
The country currently has 17 nuclear power stations - the youngest one was commissioned in 1989.
