The Japanese government on Monday issued an order to four prefectures near the quake-stricken Fukushima Daiichi nuclear power plant to halt shipments of certain food items due to the detection of abnormally high levels of radiation.

The government's orders were issued to Ibaraki, Tochigi, Gunma and Fukushima Prefectures, while a separate order from the government's nuclear disaster countermeasure headquarters was issued just to Fukushima Prefecture banning shipments of raw milk.

Radioactive substances have been detected in spinach and other green-leafed vegetables in prefectures surrounding the faltering power plant, 240 kilometers northeast of Tokyo, and as a result a number of countries are screening produce imported from Japan.

But Chief Cabinet Secretary Yukio Edano told the public on Monday that the levels of radioactivity detected in the food items would not affect the health of humans.

"The readings for radioactive substances found in the produce, despite being at levels exceeding provisional limits set under the Food Sanitation Law, aren't readings that would affect humans," Edano said.

"Even eating or drinking the contaminated foodstuffs several times would not be a health hazard," Japan's top government spokesperson said at a news conference.

Edano went on to say that as the failing nuclear power plant is owned and operated by Tokyo Electric Power Co. (TEPCO), the firm would be liable to pay "appropriate compensation" to the farmers affected by the shipment restrictions.

"Primarily, since it's a nuclear disaster, Tokyo Electric Power is supposed to be responsible," he said.

Radioactive iodine and cesium have been found in spinach and other vegetables produced in and around Fukushima at levels exceeding legal limits, following the Fukushima Daiichi nuclear power plant being severely damaged by a magnitude 9.0 earthquake quake and tsunami that struck the area on March 11.

Authorities have also advised people not to drink the tap water in a village near the Fukushima plant, following the detection of high levels of radioactive iodine in the local supply.

Low levels of radioactive substances have already been found in the water supply in Tokyo and surrounding prefectures, including Fukushima, but whilst considered abnormal the government said there was no risk to human health.