TOKYO — Japan's prime minister, fighting criticism at home over his handling of the aftermath of last month's massive earthquake and tsunami, says he deeply regrets the crisis at a radiation-leaking nuclear plant.
"I take very seriously, and deeply regret, the nuclear accidents we have had at the Fukushima Dai-ichi plant. Bringing the situation under control at the earliest possible date is my top priority," Naoto Kan said in a commentary in the weekend edition of the International Herald Tribune.
As Japan has begun planning for reconstruction and mulling how to pay for it, Kan's political opponents have resumed calls for his resignation after refraining from criticism in the immediate aftermath of the disaster.
In a show of support for a staunch American ally, U.S. Secretary of State Hillary Rodham Clinton was due to visit Tokyo briefly Sunday.
Thanking the international community for its support, Kan vowed to rebuild a country "highly resistant to national disasters."
"I pledge that the Japanese government will promptly and thoroughly verify the cause of this incident, as well as share information and the lessons learned with the rest of the world to help prevent such accidents in the future," he said in the commentary, which also appeared in the New York Times and Washington Post.
Frustrations have also been mounting over plant operator Tokyo Electric Power Co.'s failure so far to resolve Japan's worst-ever nuclear crisis, which began March 11 when the 46-foot (14-meter) tsunami knocked out power and cooling systems at the Fukushima Dai-ichi complex.
Explosions, fires and other malfunctions have interfered with efforts to repair the plant and stem radiation leaks, and officials reported late Saturday that levels of radioactivity had again risen sharply in seawater near the plant, signaling the possibility of new leaks.
Workers have been spraying massive amounts of water on the overheated reactors. Some of that water, contaminated with radiation, has leaked into the Pacific. Plant officials said they plugged that leak on April 5 and radiation levels in the sea dropped.
But samples taken Friday showed the level of radioactive iodine-131 had spiked to 6,500 times the legal limit, up from 1,100 times the limit in samples taken the day before, nuclear safety officials said. Levels of cesium-134 and cesium-137 rose nearly fourfold. The increased levels are still far below those recorded earlier this month before the initial leak was plugged.
The new rise in radioactivity could have been caused by the installation Friday of steel panels intended to contain radiation that may have temporarily stirred up stagnant waste in the area, Hidehiko Nishiyama of the Nuclear and Industrial Safety Agency told reporters. However, the increase in iodine-131, which has a relatively short eight-day half life, could signal the possibility of a new leak, he said.
"We want to determine the origin and contain the leak, but I must admit that tracking it down is difficult," he said.
Authorities have insisted the radioactivity will dissipate and poses no immediate threat to sea creatures or people who might eat them. Most experts agree.
Regardless, plant workers on Saturday began dumping sandbags filled with sand and zeolite, a mineral that absorbs radioactive cesium, into the sea to combat the radiation leaks.
Radiation has also leaked into the air, forcing the evacuation of tens of thousands of people and contaminating crops and sea products.
Government officials were fanned out across the affected areas seeking to explain evacuation decisions and calm nerves. Chief Cabinet Secretary Yukio Edano reportedly was meeting Sunday with the governor of Fukushima, who has vigorously protested the predicament the nuclear crisis poses for his prefecture.
On Saturday, his deputy, Tetsuro Fukuyama, apologized to a gathering of residents in Iitate village, parts of which the government recommended be evacuated because of the nuclear crisis.
"Everyone in the village must be extremely troubled, uncertain and worried," he said, promising to provide temporary housing and financial support.
Residents attending the meeting, many of them farmers, angrily complained, saying they could not just leave their livestock or move them elsewhere.
In the city of Inawashiro, Hiroshima University Professor Kenji Kamiya, who has been appointed an adviser to Fukushima prefecture, met with about 250 education officials to explain that radiation levels in the area do not pose an immediate or significant threat to the public.
"I hope people understand that the levels we are seeing are fairly low. Even in the most impacted areas, we have screened more than 1,000 children for radiation abnormalities in their thyroids and have found none at all," he said.
Kamiya has been giving almost daily lectures in an effort to prevent people from overreacting to the possible danger.
"People fear things that they don't understand. We were even afraid before of the rain, because we just didn't know if it was safe," said Takaaki Kobayashi, a father of two grade-school children. "I feel more comfortable now about sending kids to school. It helps to understand."
Associated Press writers Eric Talmadge in Inawashiro and Elaine Kurtenbach and Noriko Kitano in Tokyo contributed to this report.