OSAKA, Japan — Japan on Friday raised the alert level at its disaster-hit Fukushima Dai-ichi nuclear plant as teams battled round the clock to try to stabilize over-heating reactors.

The country's nuclear agency said the alert level had moved from four to five on the seven--point international scale for atomic accidents, on a par with the Three Mile Island atomic accident of 1979.

Fukushima, which was damaged by last week's 9.0-magnitude earthquake and tsunami, is now classified as an "accident with wider consequences," the BBC said.

Efforts to cool all six reactors at the plant were continuing Friday as crews, working in shifts to try to minimize radiation exposure, injected tons of seawater in a bid to avert a potentially catastrophic meltdown.

There was a glimmer of hope after engineers completed laying a power cable to connect water pumps at one of the reactors to an external electricity supply, Reuters said. Reports indicated it would by up and running on Saturday

The head of the United Nations' International Atomic Energy Agency, Yukiya Amano said Friday that the battle to bring the crippled nuclear plant under control was a "race against time," requiring global cooperation.

"This is a very grave and serious accident," he said after meeting Japan's Prime Minister Naoto Kan, AFP reported. "So it is important that the international community, including the IAEA, handles this jointly."

U.S. military officials said they were considering whether to dispatch a unit of 450 personnel trained in radiation management to help with the crisis, the Kyodo news agency reported.

On Thursday, five trucks equipped with high-pressure water cannons normally used to quell rioters sprayed tons of water at the reactor building in an attempt to cool a storage pool for spent fuel rods that has lost water and appears to be overheating.

If the worst happens, overheating fuel rods could begin to melt, releasing high levels of radiation.

The threat of a serious nuclear meltdown is fraying nerves in Tokyo, more than 150 miles south of the disabled power plant.

There is no exodus from the capital — yet — but fuel is being rationed and supermarket shelves are quickly emptied of rice, milk, noodles and other foods. Stores report a surge in demand for survival staples such as torches, batteries and sleeping bags.

Train services have been disrupted by voluntary power cuts and many employees have been told to sit out the crisis at home. A rush of transactions led to the sudden closure of thousands of ATMs at Mizuho Bank.

For all their stoicism, Tokyoites are preparing for the worse. Long lines formed outside the city's passport office, while bullet trains are filling up with a steady stream of expatriates, women and children. Television footage showed hundreds of people leaving the city on buses.

Authorities warned that Tokyo could experience a blackout on Thursday evening, but it was granted a reprieve after the operator of the plant, Tokyo Electric Power Co. (TEPCO), said demand had been lower than expected, thanks to energy-saving efforts by businesses and households.

The company claimed a victory of sorts, saying the 30 tons of water aimed at the No. 3 reactor had succeeded in cooling the storage pool. But it added that it had observed little change in radioactivity levels at the facility.

The helicopters and water cannons will resume water-bombing the plant on Friday, the firm said.

The team of technicians, firefighters and soldiers face myriad problems, but the aim is clear: to cool the No. 3 reactor and replenish the pool containing spent fuel rods.

TEPCO is unable to get close enough to take accurate readings, but it is working on the chilling assumption that the pool is almost empty, raising the risk that the fuel rods will overheat and melt.

Japanese authorities' inability to contain the damage almost a week after the tsunami coincided with a grim prognosis from nuclear experts in the United States.

Gregory Jackzo, chairman of the U.S. nuclear regulatory commission, told a congressional hearing in Washington that the storage pool at another reactor had lost all of its water and was in danger of releasing more radioactive material.

As a result, a growing number of foreign governments are taking steps to remove their citizens from danger.

The U.S. imposed an evacuation zone within a 50-mile radius of the plant and said it would send chartered aircraft to take Americans out of the country.

"We are recommending, as a precaution, that American citizens who live within 80 kilometers of the Fukushima nuclear power plant evacuate the area or to take shelter indoors if safe evacuation is not practical,'' the U.S. Embassy said in a statement.

In a rare move, the Group of Seven industrialized nations agreed to intervene in currency markets in order to reduce and stabilize the value of Japan's currency, the yen, according to an announcement Thursday night.

The move is aimed at calming global markets, which have seen a "wild week of often panic selling" after last week's disaster.