Farmers have resumed planting rice for market only 15 kilometres (nine miles) from Japan's crippled Fukushima Daiichi nuclear power plant, a local official said Wednesday.

It was the first time since the March 2011 earthquake-tsunami-nuclear disaster that farmers have gone inside the former 20-kilometre "no-go" zone around the doomed plant to sow rice intended for sale.

The zone has been redefined to let people access areas where the levels of radiation from the plant have been relatively low. Tens of thousands of people remain unable to return to their homes.

On Saturday, three farmers started planting rice seedlings in paddies over an area of six hectares (15 acres) in the city of Tamura, a Fukushima regional agriculture official said.

"The work has progressed smoothly as the weather recovered," Tsuneaki Oonami told AFP by telephone.

The rice paddies are located in Miyakoji district where a few dozen farmers used to live before they were evacuated after the devastating quake and tsunami left the plant spewing radiation from its molten reactors.

Since April last year, former residents have been permitted to re-enter the district during the daytime -- they are not allowed to stay there overnight.

"We have considerably decontaminated the rice paddies and channelled water for irrigation there," Oonami said, adding that they still have to fight "harmful rumours" about their produce.

The farmers are using fertiliser containing potassium to help curb radioactive cesium absorption by rice plants. All rice from the paddies will be checked for radioactive contamination before being shipped, said Oonami.

More than 18,000 people were killed when the huge tsunami of March 2011 swept ashore, crushing a stretch of coastline.

The nuclear disaster it sparked is not officially recorded as having directly claimed any lives, but it forced mass evacuations, with scientists warning some areas may be uninhabitable for decades.

It also polluted a swathe of prime farmland and provoked a crisis of confidence in Japan's agricultural produce.