Two explosions occurred Tuesday at Japan's quake-stricken Fukushima I power plant. Japan has asked the International Atomic Energy Agency to help it deal with its nuclear problems. Iodine supplies are being readied.
Fukushima has seen three explosions since Saturday
Two explosions hit reactors at Japan's earthquake-damaged Fukushima nuclear power complex early Tuesday, the third and fourth blasts since Saturday.
"There was a huge explosion" between 6:00 a.m. (2100 GMT Monday) and 6:15 a.m. at the number-two reactor of Fukushima I nuclear power plant, a Tokyo Electric Power Co. (TEPCO) spokesman said.
Shortly thereafter, there was an explosion at reactor number four.
Japanese Prime Minister Naoto Kan urged people within 30 km (18 miles) of the site to remain indoors, as the French embassy in Tokyo warned that low-level radioactive winds could reach the capital within 10 hours.
Japanese government spokesman Yukio Edano told reporters the suppression pool of the second nuclear reactor appeared to have been damaged in the blast. "But we have not recorded any sudden jump in radiation indicators," Edano said.
The suppression pool is the bottom part of the reactor's container which holds water used to cool it and control air pressure inside.
Authorities at the Fukushimi complex were scrambling to prevent nuclear meltdown as three reactors there suffered cooling problems.
About 185,000 people have been moved from the area
Japan has taken up an official offer of help from the UN's nuclear watchdog.
"The Japanese authorities are working as hard as they can, under extremely difficult circumstances, to stabilize the nuclear power plants and ensure safety," the head of the International Atomic Energy Agency, Yukiya Amano, said in a statement in Vienna.
Amano was a Japanese diplomat for many years before taking up his present position.
Despite being shaken, flooded and cut off from electricity, and with staff often working through immense personal tragedy, Amano said, "the reactor vessels have held and radioactive release is limited."
The continued problems were caused by Friday's devastating earthquake and tsunami. The nuclear plants shut down automatically, as they're supposed to, but power outages in the area and tsunami damage to the back-up generators is believed to have broken reactor cooling systems.
Earlier Monday, overheating in one of the other damaged reactors caused a hydrogen explosion, but the core container of the reactor had remained intact and the chances of radiation escaping were low, the government said. TV images were showing smoke belching from the plant, located 240 kilometers (150 miles) north of Tokyo.
Authorities have declared an evacuation zone within a 20-kilometer radius of the plant, displacing roughly 185,000 people.
"We have strongly advised all the people within the evacuation area to go inside nearby facilities," said Ryo Miyake, spokesman for the nuclear safety agency.
The quake was the worst in Japanese history
As a precautionary measure, the IAEA said Japan had distributed 230,000 units of stable iodine to evacuation centers around the affected nuclear plants. If someone is exposed to radiation in a nuclear accident, iodine can help to protect against thyroid cancer.
Death toll rises
Police officials estimate the death toll from Friday's 8.9-magnitude earthquake and tsunami to have exceeded 10,000, with tens of thousands still unaccounted for. The earthquake was the biggest since Japan started keeping records, 140 years ago.
"The earthquake, tsunami and the nuclear incident have been the biggest crisis Japan has encountered in the 65 years since the end of World War II," Japanese Prime Minister Naoto Kan told a news conference on Sunday.
Kan maintained, however, that the ongoing nuclear emergency was not another Chernobyl in the making.
"Radiation has been released into the air, but there are no reports that a large amount was released," he said. "This is fundamentally different from the Chernobyl accident."
Authorities are desperately trying to avoid a nuclear disaster by venting radioactive steam into the air to relieve pressure on the reactors. They are also pouring sea water into the reactors to cool them down.
190 people have been exposed to radiation, according to officials
The United States sent two rescue teams and a pair of nuclear energy experts to Japan. The search teams from Fairfax, Virginia, and Los Angeles include more than 140 personnel, sniffer dogs and equipment to help with rescue efforts.
Germany's Disaster Relief Agency (THW) has sent 44 men and women to help with search and rescue efforts.
The United Nations put 30 disaster response teams on alert to help Japan if needed.
Authors: Nicole Goebel, Matt Zuvela, Mark Hallam (Reuters, dpa, AP, AFP)
Editor: Michael Lawton