An 80-year-old woman and a 16-year-old boy have been rescued from a badly damaged house in Ishinomaki, Miyagi Prefecture, nine days after the magnitude 9 earthquake and subsequent tsunami ravaged the area, the Japan Times reports.

Sumi Abe and her grandson Jin were found yesterday by local police officers looking for survivors in the coastal city. The boy was found on the roof of the house and told the police his grandmother was inside.

The pair were taken to Ishinomaki Red Cross Hospital but sustained no injuries, although Jin suffered hypothermia.

Jin told authorities they had been stranded in the demolished house since the March 11 quake, surviving off yogurt, water and Coca-Cola, Japan Times said.

Quake toll likely to reach 20,000

Last night, Japan raised the toll of the quake and tsunami to 20,000 dead and missing, with tens of thousands more feared dead.

Around 8,277 people have been confirmed dead and 12,722 have been reported missing.

Unprepared for nuclear disaster

Meanwhile Japanese officials yesterday admitted the government had not reacted quickly enough to aid those living near the stricken nuclear power station at Fukushima.

Radiation has seeped into the food supply, with the government saying that tests of spinach and milk from areas 120km away had exceeded safety limits. Tiny amounts of radioactive iodine were detected in tap water in Tokyo and other areas.

The statement came after a nuclear safety official said the government only belatedly realised the need to give potassium iodine to those living within 20km of the nuclear complex.

The pills help reduce the chances of thyroid cancer, which can develop with exposure to radiation.

The official, Kazuma Yokota, said an explosion at the plant's Unit 3 reactor on Sunday last week should have triggered the distribution. But the order only came three days later.

"We should have made this decision and announced it sooner. It is true we had not foreseen a disaster of these proportions. We had not trained for something this bad. We must admit that we were not fully prepared."

More radiation to be released

An official had said a larger amount of radiation than a week ago would have to be released because more nuclear fuel had degraded since then.

But Tokyo Electric Power Company said that while pressure was high, there was no immediate need to vent.

Power has been restored to Unit 2 and the plants operators will attempt to turn on its cooling systems to bring the overheating reactor under control.

There was no guarantee the cooling systems would still work.

Pressure in the unit 3 containment vessel, however, remains high but has stabilised, and Tepco has decided against releasing gases from the reactor.

Unit 3 is the only reactor to use plutonium - the highly radioactive material that remains toxic for tens of thousands of years - in its fuel mix.

Units 5 and 6 have now been placed into cold shutdown, meaning the reactors are in a safe mode, with cooling systems stable and under control, and with low temperature and pressure within the reactor, Japanese officials say.

An operation to douse unit 4 with sea water was completed yesterday, with more than 100 tonnes of water sprayed on the unit - much of it reaching inside the damaged reactor.