Japan Latest: The Crisis at the Nuclear Plant

1611 GMT: The situation at the nuclear plants is urgent, indeed. Reuters has this flash update:

"IAEA head says core damage at units 1-3 of Japan's quake-hit nuclear plant confirmed, situation very serious"

1510 GMT: The mayor of Ishinomaki, in Miyagi Prefecture in northeast Japan, says it is likely that 10,000 are missing from the town.

The International Atomic Energy Agency says #Japanese authorities are concerned over the condition of pools for spent nuclear fuel pools at the Fukushima No. 3 and No. 4 nuclear reactor complexes.

0945 GMT: The New York Times summarises the situation at the Fukushima nuclear plant:

The authorities announced that a second reactor unit at the stricken Fukushima Daiichi plant in northeastern Japan may have ruptured and appeared to be releasing radio steam.

Such were the radiation levels above the plant, moreover, that the Defense Force put off a highly unusual plan to dump water from military helicopters to lower temperatures in an overheating pool containing spent fuel rods, news reports said.

The development showed the seriousness of the challenges facing the authorities. The vessel that possibly ruptured had been seen as the last fully intact line of defense against large-scale releases of radioactive material from one of the stricken reactors, but it was not clear how serious the possible breach might be. The implications of overheating in the fuel rod pool at the plant’s No. 3 reactor unit also seemed perilous.

Water bombs were dropped onto the site of a fire in the No. 4 reactor complex, but the plan was abandoned. The complex is now being doused with water.

0755 GMT: Emperor Akahito has addressed the nation on television. He says that events were unexpected and victims should never lose hope and take care of their health.

State broadcaster NHK is now reporting that  more than 11,000 people have died or are missing in the earthquake and tsunami.

0545 GMT: Japan has ordered workers to leave the damaged Fukushima nuclear plant as radiation rises to dangerous levels. A skeleton crew remains.

White smoke is still rising from Fukushima after fire was reported last night at the No. 4 reactor compl. Officials have considered dropping water or boric acid from helicopters to control the flames.

The official death toll for Friday's earthquake and tsunami is now 3,570, with "thousands" still missing.