Engineers enjoyed some success in their mission to stop disaster at Japan's tsunami-damaged power plant, though minor radiation leaks highlighted perils from the world's worst nuclear crisis since Chernobyl 25 years ago.
Three hundred technicians have been battling inside a danger zone to salvage the six-reactor Fukushima plant since it was hit by an earthquake and tsunami that also killed 7,508 people and left 11,700 more missing in northeast Japan.
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The unprecedented multiple crisis will cost the world's third largest economy nearly $200 billion in Japan's biggest reconstruction push since post-World War II.
It has also set back nuclear power plans the world over.
Encouragingly for Japanese transfixed on the work at the Fukushima complex, the situation at the most critical reactor -- No. 3 which contains highly toxic plutonium -- appeared to come back from the brink after fire trucks doused it for hours.
Work also advanced on bringing power back to water pumps used to cool overheating nuclear fuel.
"We are making progress ... (but) we shouldn't be too optimistic," said Hidehiko Nishiyama, deputy-general��at Japan's Nuclear Safety Agency.
Engineers attached a power cable to the No.1 and No. 2 reactors, hoping to restore electricity later in the day prior to an attempt to switch the pumps on.
They aim to reach No. 3 and 4 soon after that.
If successful, that could be a turning point in a crisis already rated as bad as America's 1979 Three Mile Island accident.
If not, drastic measures may be required such as burying the plant in sand and concrete as happened at Chernobyl after the world's worst nuclear reactor disaster in 1986.
Cooling systems have been restored at the least critical of the six reactors, No. 5 and 6, using diesel generators.
In the face of mounting criticism, plant operator TEPCO's president issued a public apology for "causing such great concern and nuisance".
Experts said even after restoring power, the company faces a tricky task in reactivating the cooling pumps at the plant , with parts of the system probably broken from quake damage or the subsequent hydrogen explosions.
"The workers need to go through the plant, figure out what survived and what didn't, what can be readily repaired and get the cooling systems back up and running to deal with the cores and the spent��fuel pools," said David Lochbaum, of U.S. nuclear watchdog the Union of Concerned Scientists.
Russia's Prime Minister Vladimir Putin gave some international recognition to Japan's progress during a trip to reassure residents of eastern regions that there was no immediate danger from the nuclear accident.
"Our Japanese colleagues are gradually, not right away and with mistakes... getting the situation under control," he said i n the city of Yuzhno-Sakhalinsk. "The work is being done properly, in the right way -- 24 hours a day."
On the negative side, evidence has begun emerging of radiation leaks from the plant, including into food and water.
Though public fear of radiation runs deep, and anxiety has spread as far as the Pacific-facing side of the United States, health officials say levels so far are not alarming.
Traces exceeding national safety standards were, though, found in milk from a farm about 30 km (18 miles) from the plant and spinach grown in neighbouring Ibaraki prefecture.
Tiny levels of radioactive iodine have also been found in tap water in Tokyo, one of the world's largest cities about 240 km (150 miles) to south. Many tourists and expatriates have already left and residents are generally staying indoors.
The sample contained 1.5 becquerals per kg of iodine 131, well below the tolerable limit for food and drink of 300 becquerals per kg, the government said.
Japan said the traces so far found posed no risks.
Yet U.N. atomic watchdog the International Atomic Energy Agency said Japan was considering whether to halt all food product sales from Fukushima prefecture.
The first discovery of contaminated food since the March 11 disaster is likely to heighten scrutiny of Japanese food exports, especially in Asia, their biggest market.
Prime Minister Naoto Kan, who has kept a low profile during the crisis except for shouting at plant operator Tokyo Electric Power Co (TEPCO), sounded out the opposition about forming a government of national unity to deal with the crisis.
But the largest opposition party rejected that.
Showing the incredible power of the 9.0 magnitude earthquake, the largest in tremor-prone Japan's recorded history, Oshika peninsula in Miyagi prefecture shifted a whole 5.3 metres (17 ft) east and its land sank 1.2 metres (4 ft).
In contrast to the generally traumatic and negative images so far, one video emerged showing the crew of a Japanese coastguard vessel successfully riding a massive wave by turning the bow directly at the wall of waters.
The quake and ensuing 10-metre high tsunami devastated Japan's north east coastal region, wiping towns off the map and making some 3 6 0,000 people homeless in a test for the Asian nation's reputation for resilience and social cohesion.
Food, water, medicine and fuel are short in some parts, and low temperatures during Japan's winter are not helping.
The traumatic hunt for bodies and missing people continues.
"This morning my next door neighbour came crying to me that she still can't find her husband. All I could tell her was, 'We'll do our best, so just hold on a little longer,'" said fire brigade officer Takao Sato in the disaster zone.
About 257,000 households in the north still have no electricity and at least one million lack running water.
(Additional reporting by Elaine Lies, Tomasz Janowski in Tokyo, and Yoko Kubota and Chang-ran Kim in Rikuzentakata; Alister Doyle in Oslo; Gleb Bryanski in Yuzhno-Sakhalinsk, Russia; Eileen O'Grady in Houston; Writing by Andrew Cawthorne. Editing by Jeremy Laurence)