Japan asked the International Atomic Energy Agency (IAEA) for help Monday in dealing with its nuclear accident following the massive earthquake.

IAEA chief Yukiya Amano told agency member states in Vienna that details of the mission were still being discussed with Japan, DPA reported.

Amano also commended Japan for its efforts in trying to deal with its reactors at the Fukushima power plant, where the cooling system is damaged.

"The reactor vessels have held and radioactive release is limited," he said.

Media reports say fuel rods in the number 2 reactor at the Fukishima nuclear facility are again "fully exposed" boosting fears of an eventual partial meltdown.

The head of the U.N. nuclear watchdog Yukiya Amano said the massive earthquake and tsunami had shaken and flooded nuclear power plants but their reactor vessels remained intact and radiation release was limited.

"The Japanese authorities are working as hard as they can, under extremely difficult circumstances, to stabilize the nuclear power plants and ensure safety" Amano said in a statement.

Three nuclear facilities in Japan – Fukushima, Onagawa, and Tokai – have faced serious technical problems as a result of earthquake damages.

The situation in Fukushima is the most problematic. The authorities have evacuated a total of 210 000 living within a 20 km radius of the Fukushima NPP, which is located 250 km north of Tokyo.