The situation at the heavily damaged Fukushima nuclear plant in northeastern Japan has been described as serious but "reasonably stable," as efforts were made to restore control over the reactor cooling system.
Engineers at the plant worked through Thursday night to lay a kilometer-long (0.6 mile) cable from the main electricity grid to reactors number one and two in an effort to restart water pumps on the site. Operator TEPCO said it hoped to finish work on the power lines by Friday.
The plant was hit hard in Friday's 9.0-magnitude earthquake off Japan and the subsequent tsunami that battered coastal cities.
Meanwhile, military fire trucks were on hand Friday to cool the overheating reactor Number 3 if requested.
Four military helicopters had been emptying containers of water onto reactors three and four earlier Thursday to prevent potential nuclear meltdown. More than 30 tons of water were aimed at reactor Number 3 on Thursday morning alone. High radiation levels had earlier prevented helicopters from carrying out the operation.
Graham Andrew of the International Atomic Energy Agency (IAEA) said late Thursday "the situation remains very serious but there has been no significant worsening since yesterday."
However, Andrew warned that it was still possible for the situation to deteriorate.
On Wednesday, workers had to be temporarily evacuated from the plant after radiation levels went up to 1,000 millisieverts per hour. Experts say a single dose of 1,000 millisieverts can cause radiation sickness.
It remained unclear whether the inner containment shells of the reactors had been damaged. Chief government spokesman Yukio Edano has said there was no definitive information about the containment shells but conceded that radioactive steam might have leaked in recent days.
Emergency officials have set up a 20-kilometer exclusion zone around the Fukushima complex, while US nuclear authorities recommended against remaining within 80 kilometers of the site.
US President Barack Obama told Japanese Prime Minister Naoto Kan his country would give any support Japan needed for mid- and long-term reconstruction.
The head of the International Atomic Energy Agency, Yukiya Amano, has described the situation as very serious.
The increasing concern about whether a catastrophic meltdown can be averted has led more governments to issue warnings or make arrangements to evacuate their nationals.
Both the United States and Britain announced that they were chartering planes to bring their citizens out of Japan, while France said it would send two government aircraft. Commercial airline tickets are scarce as many foreign nationals try to leave on their own.
Germany's foreign office advised its nationals in the Tokyo and Yokokama areas to head south to Osaka or to leave the country entirely through Osaka. It also advised Germans to avoid non-essential travel to Japan.
Apart from the nuclear crisis, the Japanese government was also dealing with the after-effects of the deadly earthquake and tsunami that has left hundreds of thousands homeless. Almost 15,000 people were believed to be dead or missing late on Thursday. The confirmed death toll stands at 5,892.
Author: Darren Mara, Chuck Penfold, Richard Connor (AFP, dpa Reuters)
Editor: Michael Lawton