Following the move of the United States, Australia also imposed restrictions on some food products from Japanese prefectures near the stricken Fukushima nuclear plant.

The restrictions cover milk and milk products, fresh fruit and vegetables, seaweed and seafood, Food Standards Australia New Zealand said today on its website.

The agency made the decision after the Japanese government restricted certain foods produced in areas exposed to radiation.

It said risks to Australian consumers remained negligible, adding it was a "precautionary measure, and consistent with approaches internationally".

"Milk and milk products and fresh produce are not imported into Australia, while imports of seaweed and seafood represent a very small proportion (5.5 per cent and 0.46 per cent respectively) of Australia's total imports of these products," the agency said.

The move follows action by other countries including the US and the Chinese state Hong Kong, which barred milk and fresh produce from four Japanese prefectures yesterday.

Early this week, the Japanese ministry of health, labour and welfare confirmed the presence of radioactive iodine in dairy, produce and infant formula five times the acceptable level for public health and prevented the shipment of these products within and outside the country.

"Though radioactive iodine has a short half-life of about eight days and decays naturally within a matter of weeks, there is a risk to human health if radioactive iodine in food is absorbed into the human body," the US Food and Drug Administration said. "If ingested, it can accumulate in and cause damage to the thyroid."

"Children and young people are particularly at risk of thyroid damage due to the ingestion of radioactive iodine," the FDA said.