People living in areas contaminated most by radioactive material released by the Fukushima Daiichi nuclear disaster two years ago in Japan have a higher risk of developing cancer over their lifetime, the World Health Organisation (WHO) has said.

The UN agency released a 200-page report on Thursday saying it "estimates that the lifetime risk for some cancers may be somewhat elevated above base-line rates in certain age and sex groups that were in the areas most affected".

A 9.0 magnitude earthquake and tsunami on March 11, 2011, killed nearly 19,000 people and devastated the Daiichi nuclear plant, triggering meltdowns and spewing radiation. At least 160,000 people were forced to flee their homes.

"A breakdown of data, based on age, gender and proximity to the plant, does show a higher cancer risk for those located in the most contaminated parts," Maria Neira, WHO director for public health and environment, said in a statement.

In the most contaminated area, the WHO estimated that there was a 70 percent higher risk of females exposed as infants developing thyroid cancer over their lifetime.

The thyroid is the most exposed organ as radioactive iodine concentrates there and children are deemed especially vulnerable.

The report concluded that for the general population inside Japan, the predicted health risks were low, but that one-third of emergency workers were estimated to have increased risk.

But there was no discernible increase in health risks expected outside Japan, the WHO said in the report, which was based on a comprehensive assessment by international experts.