The owner of the damaged Fukushima Dai-ichi nuclear power plant announced Sunday a long-term plan to contain radioactive leaks and bring the crisis under control within six to nine months.

Tokyo Electric Power Co. chairman Tsunehisa Katsumata told at a news conference that the company had come up with a phased road map for ending the crisis and allowing residents evacuated from the area around the facility to return home. 

Officials said the plan involved covering the damaged reactor buildings to contain the radiation.

In the first three months of the plan, the company hopes to steadily reduce the level of leaking radiation, Katsumata said. Three to six months after that, it hopes to get the release of radioactive materials under control.

To contain radioactive levels, TEPCO plans to install a new cooling system that filters contaminated water and then recirculates clean water back into the reactors, Japanese broadcaster NHK reports. The water is planned to be pumped outside for safe removal of radioactive substances and salt before the treated water is then circulated back into the reactors.

But the new system won't be operational until summer, according to NHK.

The company is also focusing on mitigating the release of radiation into the atmosphere and soil and measuring and reducing the amount of radiation effecting the evacuation area, Katsumata said.

"I believe we will succeed in containing the crisis," Katsumata said.

The company also outlined plans for permanently covering the buildings and closing down the reactors, but that will take years, officials said.

Kaieda, the trade minister, said he hoped to see the process quickly "shift from the first aid phase to a systematic and stable phase."

On Saturday, levels of radioactivity rose sharply signaling the possibility of new leaks at the facility, the government said.

The level of radioactive iodine-131 spiked to 6,500 times the legal limit, according to samples taken Friday, up from 1,100 times the limit in samples taken the day before. 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 announcement came after a magnitude-5.9 earthquake jolted Japan on Saturday morning, hours after the country's nuclear safety agency ordered plant operators to beef up their quake preparedness systems to prevent a recurrence of the nuclear crisis.

There were no reports of damage from the earthquake, and there was no risk of a tsunami similar to the one that struck the Fukushima Dai-ichi plant.

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 zeolite, a mineral that absorbs radioactive cesium, into the sea to combat the radiation leaks.

Meanwhile, the newspaper Asahi Shimbun reported, without citing its sources, that a secret plan to dismantle Tokyo Electric Power Co., which runs the radiation-leaking Fukushima plant, was circulating within the government. The proposal calls for putting TEPCO, the world's largest private electricity company, under close government supervision before putting it into bankruptcy and thoroughly restructuring its assets. Most government offices were closed Saturday, and the report could not be immediately confirmed.

In the wake of the nuclear crisis, the government ordered 13 nuclear plant operators to check and improve outside power links to avoid earthquake-related outages that could cause safety systems to fail as they did at the Fukushima plant, Nishiyama told reporters late Friday. The operators, including TEPCO, are to report back by May 16.

Power outages during a strong aftershock on April 7 drove home the need to ensure that plants are able to continue to operate crucial cooling systems and other equipment despite earthquakes, tsunamis and other disasters, Nishiyama said.

Utility companies were ordered to reinforce the quake resistance of power lines connected to each reactor or to rebuild them. They also must store all electrical equipment in watertight structures. Earlier, the nuclear agency ordered plant operators to store at least two emergency backup generators per reactor and to install fire pumps and power supply vehicles as further precautions.

The massive 46-foot wave that swamped Fukushima Dai-ichi last month knocked out emergency generators meant to power cooling systems. Since then, explosions, fires and other malfunctions have compounded efforts by TEPCO to repair the plant and stem radiation leaks.

TEPCO said Saturday it had moved power sources for some of the reactors at the stricken plant to higher ground by Friday evening in order to avoid another disastrous failure in the event of a tsunami.

The crisis at the Fukushima plant has forced tens of thousands of people to evacuate the area, while radiation leaks have contaminated crops and left fishermen unable to sell their catches, adding to the suffering of communities already devastated by earthquake and tsunami damage.

In the city of Inawashiro, Hiroshima University Professor Kenji Kamiya, who has been appointed a health risk 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.

The Associated Press contributed to this report.