Japan has said it will ban anyone entering the 12 mile evacuation zone around the Fukushima Daiichi nuclear plant.
Tens of thousands of people were evacuated after the earthquake smashed the facility, operated by Tokyo Electric Power (TEPCO).
However many have returned to collect belongings as TEPCO struggles to contain the nuclear crisis..
People will only be able to go into the zone under government supervision, chief cabinet secretary Yukio Edano said.
"We will take strict legal measures against those trying to enter the area," he said.
"For residents, all I can say is I ask for their understanding so that no legal action will be taken against them."
Anyone breaking the ban can be fined up to 100,000 yen (£736) or face temporary detention by police.
More than 130,000 people are still living in shelters more than a month after the earthquake and tsunami that left some 28,000 dead or missing.
TEPCO wants a "cold shutdown" of the Fukushima Daiichi plant within six to nine months which experts say will be tough to meet.
Highly contaminated water is being pumped from one of the reactors, a key step towards repairing the cooling system that regulates the temperature of radioactive fuel rods.
Water levels however were unchanged, one of several problems engineers have faced since the crisis began, which has included pumping radioactive water into the sea.
The amount of radiation included in water released earlier this month into the sea was at 20,000 times the amount Japan's Nuclear and Industrial Safety Agency allows for the plant to release outdoors annually.
Japan Prime Minister Naoto Kan, criticised by government ministers for his handling of the nuclear crisis, has expressed "extreme regret" and said Japanese goods were still safe.
TEPCO insists that while fuel rods at three of its six reactors were damaged when they partially melted after the quake, they are not in "meltdown".