The Japanese government has ordered a halt to all shipments of spinach from four prefectures surrounding the country's tsunami-damaged nuclear power plant and banned milk shipments from the site's home province of Fukushima.
A 9.0-magnitude earthquake on 11 March triggered a tsunami that devastated the country's north-eastern coast and hit the Fukushima plant, triggering a nuclear emergency.
Chief Cabinet Secretary Yukio Edano announced the measures at a briefing on Monday, amid increasing concerns over contamination of some foods and tap water with trace amounts of radioactivity.
China and South Korea have announced they will toughen checks of Japanese food for radioactivity, Reuters reports.
The World Health Organisation has said the detection of radiation in some food in Japan was a more serious problem than it had expected.
However, it said it had no evidence of contaminated food spreading internationally.
Japanese officials have told residents in one town 40km from the plant to stop drinking tap water after high levels of radioactive iodine were detected. The government is reportedly preparing to hand out bottled water instead.
Contaminated food has been found further afield, including in the city of Hitachi, more than 100km south of Fukushima, the ABC reports.
In Hitachi, officials discovered spinach with radiation levels 27 times the legal limit.