TOKYO - In the Japanese city of Ohtawara, more than 100 km (62 miles) southwest of the crippled Fukushima nuclear plant, 400 tonnes of  radioactive ash have piled up at a garbage incineration plant, which will run out of protected storage space in two weeks.

Further south, the city of Kashiwa has been forced to temporarily shut a high-tech incinerator because its advanced technology that minimises the amount of ash produced has the side-effect of boosting the concentration of radiation.

Ohtawara and Kashiwa are just two of a growing number of municipalities across northern Japan that face similar problems after the Fukushima Daiichi atomic power plant, devastated by a huge March quake and tsunami, began spewing radiation into the atmosphere in the world's worst nuclear accident in 25 years.  

Although the government aims to bring the Fukushima crisis under control by December, researchers say that problems arising from the radiation, scattered over mountains, rivers and residential areas, are set to persist for years.

"Residents say they are worried about their children's health and grandchildren's health. Faced with such pleas, we just cannot make a move," an Ohtawara city official said, explaining why the ash has not be taken to a nearby city dump.

Ohtawara has already cut the frequency of garbage collection by half to hold down the generation of radioactive ash, by-product of burning contaminated leaves and branches.  

Nonetheless, fresh bags of radioactive ash will have to be left in empty outdoor space at the incineration facility with no proper shelter around them, the official said.