The World Health Organization (WHO) said Saturday that the public health risk from Japan's radiation leak appeared to be "quite low" but the WHO network of medical experts was ready to assist if requested.

"At this moment it appears to be the case that the public health risk is probably quite low. We understand radiation that has escaped from the plant is very small in amount," World Health Organization spokesman Gregory Hartl told Reuters.

Radiation leaked from an earthquake-crippled nuclear plant in Japan Saturday after a blast blew off the roof, and authorities were preparing to distribute iodine to local people to protect them from exposure.