The US Food and Drug Administration says it will halt imports of dairy products and produce from the area of Japan where a nuclear reactor is leaking radiation.
The FDA said on Tuesday that those foods will be detained at entry and will not be sold to the public. The agency previously said it would just step up screening of those foods.
Other foods imported from Japan, including seafood, will still be sold to the public but screened first for radiation.
Japanese foods make up less than 4 per cent of all US imports, and the FDA has said it expects no risk to the US food supply from radiation.
Japan PM halts farm shipments near nuke plant
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Japan's Prime Minister Naoto Kan has ordered two prefectures affected by radiation leaks from the stricken Fukushima nuclear plant to stop shipping a range of farm products, AFP reports.
Kan told prefectural governors to halt shipments of "komatsuna" green leaf vegetables and broccoli from Fukushima, and untreated milk and parsley from neighbouring Ibaraki, Jiji Press and other media said.
Public broadcaster NHK said Kan had also told people in those areas not to eat the vegetables, which were found to have abnormal radiation levels because of releases from the nearby crippled nuclear power plant.
Japan's Fukushima Dai-ichi nuclear complex has been leaking radiation after it was damaged in a devastating earthquake and tsunami in Japan this month.
Aftershocks rattle nuclear plant
Strong aftershocks hit near the troubled nuclear power plant at the centre of Japan's radiation crisis today, the meteorological agency said.
The agency said there was no fear of a tsunami following the two quakes, whose magnitude were recorded at 6.0 and 5.8 by the agency.
Public broadcaster NHK said there was no immediate report of further damage to nuclear power plants in Fukushima, including the Fukushima No. 1, which was crippled by the March 11 quake and tsunami.
An external electricity supply has now been linked up to all six reactors at the Fukushima No. 1 power station, more than a week after a 14-metre (46-foot) tsunami hit the ageing facility.
In another small step towards regaining control of the plant, the lights came back on in the control centre of the number three reactor, making it easier for workers toiling to get the vital cooling systems working again.
