Japan earthquake: Radiation levels fall at Fukushima
Radiation levels have fallen at Japan's earthquake-stricken Fukushima Daiichi nuclear plant, the government says.
The levels had spiked to harmful levels after a fire and two more explosions at the site.
Weather reports say winds are blowing radiation from the plant, on Japan's north-east coast, over the Pacific.
Friday's 9.0-magnitude quake and tsunami devastated Japan's north-east coast, with more than 3,000 confirmed dead and thousands missing.
Officials have warned people within 20-30km of the nuclear plant to either leave the area or stay indoors.
Japan has also announced a 30-km no-fly zone around the site to prevent planes spreading the radiation further afield.
Further strong aftershocks continue to rock the country. An earthquake, not considered an aftershock, of magnitude 6.2 centred south-west of Tokyo shook buildings in the capital.
Friday afternoon's earthquake was the strongest in Japan since records began to be kept. It hit the north-east of the main island of Honshu and triggered a powerful tsunami that devastated dozens of coastal communities.
The latest official death toll from the quake and tsunami stands at more than 3,000 - but thousands of people are missing and it is feared at least 10,000 may have been killed.
More than 500,000 people have been made homeless.
The government has deployed 100,000 troops to lead the aid effort.
The crisis at the Fukushima plant - which contains six nuclear reactors - has mounted since the earthquake knocked out the cooling systems.
Explosions rocked the buildings housing reactors one and three on Saturday and Monday.
On Tuesday morning a third blast hit reactor two's building.
The plant's operator, Tokyo Electric Power Co, said another explosion damaged reactor's four building, where a fire also broke out in the unit's spent fuel storage pond.
It had been shut down before the quake for maintenance, but its spent nuclear fuel rods were stored on the site.
Officials said the explosions at the first three reactors, and possibly the fourth as well, were caused by a buildup of hydrogen.
Chief Cabinet Secretary Yukio Edano said they were closely watching the remaining two reactors at the plant, five and six, as they had begun overheating slightly.
He said cooling seawater was being pumped into reactors one and three - which were returning to normal - and into reactor two, which remained unstable.
The repeated releases of different amounts of radiation - some large, some small - are unnerving the Japanese and their neighbours, who want reassurances that the situation will soon be brought under control, says the BBC's Chris Hogg in Tokyo.
Japan's nuclear safety agency said earlier it suspected the blast may have damaged reactor two's suppression chamber, which would have allowed radioactive steam to escape.
The head of the UN's nuclear agency, Yukiya Amano, said there was a "possibility" reactor two's core had been damaged, but he added that Tuesday's increase in radiation levels was due to the fire at reactor four.
After the explosions and fire, radiation dosages of up to 400 millisieverts per hour were recorded between reactors three and four at the Fukushima Daiichi site, about 250km north-east of Tokyo.
A single dose of 1,000 millisieverts causes temporary radiation sickness such as nausea and vomiting.
Later, a reading of 0.6 millisieverts (mSv) per hour was made at the plant's main gate, the International Atomic Energy Agency said.
The IAEA's Amano also said Japan should provide more information: "The communication needs to be strengthened. I have asked the Japanese counterparts to further strengthen and facilitate their communication."
Europe's energy commissioner Guenther Oettinger said Tokyo had almost lost control of the situation at Fukushima.
"There is talk of an apocalypse and I think the word is particularly well chosen," he told the European Parliament.
Radiation levels in the Japanese capital - 250km away - were reported to be higher than normal earlier on Tuesday before falling. Officials said there were no health dangers.
Tokyo residents have been stocking up on supplies, with some stores selling out of items such as food, water, face masks and candles.
Mariko Kawase, 34, told AFP news agency: "I am shopping now because we may not be able to go out due to the radiation."
Three other nuclear power plants shut down automatically during Friday's earthquake and are in a safe and stable condition, the IAEA reported on Tuesday.
The loss of so much generating capacity in one blow has meant rolling blackouts have had to imposed on parts of the country.
In other developments:
- An elderly man was pulled out from a collapsed building in Ishinomaki in Miyagi prefecture, 96 hours after the disaster
- A 70-year-old woman was rescued after 92 hours from rubble in the coastal town of Otsuchi
- China began evacuating citizens from north-east Japan
- Bone marrow transplant centres across Europe have been asked to be on standby to treat Japanese radiation victims if needed
The UK Foreign Office has updated its travel advice to warn against all non-essential travel to Tokyo and north-eastern Japan. British nationals and friends and relatives of those in Japan can contact the Foreign Office on +44(0) 20 7008 0000.