Water in Tokyo is showing hazardous levels of radiation for infants, while the United States has become the first nation to block food imports.
Authorities in Tokyo said water at a purification plant for the capital of 13m people had 210 Becquerels of radioactive iodine - more than twice the safety level for infants.
'This is without doubt, an effect of the Fukushima Daiichi plant,' a Tokyo metropolitan government official said, in reference to the damaged nuclear plant 250km north of the city.
Tokyo governor Shintaro Ishihara, however, said the radiation level posed no immediate health risk and water could still be used.
'But for infants under age one, I would like them to refrain from using tap water to dilute baby formula,' he said.
The US Food and Drug Administration has meanwhile said it was stopping imports of milk, vegetable and fruit from four prefectures in Japan's crisis-hit northeast.
South Korea may be next to ban Japanese food after the world's worst atomic crisis since Chernobyl in 1986.
France this week asked the European Commission to look into harmonising controls on radioactivity in imports from Japan.
At the six-reactor Fukushima plant, crippled by the 11 March earthquake and tsunami, engineers are battling to cool reactors to contain further contamination and avert a meltdown.
Smoke has again disrupted efforts to regain control of the nuclear plant, where engineers were close to restoring a water pump at one of the reactors.
Workers were pulled back after a plume of dark smoke rose from the No 3 reactor unit.
An official from the International Atomic Energy Agency said the 'overall situation remains of serious concern'.
In a rapidly widening problem, Japan said today above-safety radiation levels had been discovered in 11 types of vegetables from the area, in addition to milk and water.
Officials still insisted, however, that there was no major danger to humans and urged the world not to over react.
'We will explain to countries the facts and we hope they will take logical measures based on them,' Japan's chief cabinet secretary Yukio Edano told a news conference.
The Asian nation's worst crisis since WWII may have caused $300bn damage and sent shock waves through global financial markets.
It left nearly 23,000 people dead or missing, mostly from flattened coastal towns.
More than 250,000 people are living in shelters, while rescuers and sniffer dogs comb debris and mud looking for corpses and personal mementoes.
Irish in Japan
12 Irish citizens were in the affected area when the tsunami struck Japan.
Tánaiste and Foreign Affairs Minister Eamon Gilmore told the Dáil today that none of them suffered serious injury or loss.
Speaking during a special statements session, he praised the staff of the Irish embassy there.
He said the Department had advised Irish citizens near the affected area on the main island of Japan to leave the country.
On the issue of aid, Minister Gilmore said Irish emergency stockpiles had been made available to Japan and that expert teams were also available.
Ireland had given €1m to the Japan Red Cross, he added.
