Japanese health workers have begun checking more than 300,000 children living near the Fukushima nuclear plant for thyroid abnormalities.

Parents have expressed concern about a link between thyroid abnormalities and radiation, citing reports of a rise after Chernobyl in 1986.

The Fukushima plant was crippled by the earthquake and tsunami in March which killed 20,000 people.

Concerns remain high over the possible effects of any lingering contamination.

The tests began after an unofficial survey which found that 10 out of 130 children evacuated from Fukushima had hormonal and other irregularities in the thyroid glands, according to AFP news agency.

But those who conducted the survey said they could not establish a link between the irregularities and Japan's nuclear crisis.