A plastic shopping bag, containing 10 million yen, was found on September 22 in a toilet for disabled people in the city hall of Sakado, a commuter town north of Tokyo, a city official told AFP.

The city will give the money to the Japanese Red Cross if the anonymous donor doesn't reclaim it within three months, city spokeswoman Masumi Sekiguchi said.

She said a hand-written note was attached to the cash, reading: "I'm all alone. I have no future so let the people in Tohoku use it."

Tohoku is the country's northeast region devastated by the catastrophe that killed 20,000 people and triggered an emergency at the Fukushima Daiichi nuclear power plant.

"There was no witness to the act and we cannot guess what kind of person has been involved," she said. "We were really surprised. We also feel thankful for such kindness."