It found that chemical weapons had been abandoned in nearly 140 locations throughout the country.

The survey was carried out after several poisoning incidents, including the discovery that drinking water in a town north of Tokyo was contaminated with arsenic.

It was believed to have leaked from an abandoned military stockpile.

The Environment Ministry says measures will be taken to detect and deal with any further contamination.

Earlier this year a Japanese court awarded more than $1.5m in compensation to Chinese victims of chemical and other weapons left behind after the Japanese occupation of China and the Korean peninsula.