More than 100 South Korean schools have cancelled or shortened classes over fears that rain falling across the country may show traces of radiation from the Fukushima nuclear plant in Japan.

The Education Office of Gyeonggi province said it allowed schools to decide whether to open on Thursday.

The prime minister's office said radiation levels in the rain were low and posed no health threat.

But officials said that 126 schools in Gyeonggi province near Seoul closed, and 43 others shortened class hours as a precaution.

The Ministry of Education, Science and Technology said only a few schools outside Gyeonggi cancelled classes on Thursday.

Radiation levels are falling sharply as you move away from the source, and officials have cleared the 12-mile radius aroundthe Fukushima Dai-ichi nuclear complex.

Recent progress at the plant, which was damaged by the earthquake and subsequent Tsunami on 11 March, appears to have slowed the release of radiation into the ocean. This week, technicians plugged a crack that had been gushing contaminated water into the Pacific Ocean.

Contamination in waters off the coast has fallen dramatically since then.