An elderly Japanese man has anonymously donated his life's savings -- in cash -- to a city outside of Tokyo, an unexpected financial windfall as the economy reels from the fallout of the coronavirus pandemic.

The man, who did not identify himself, appeared at city hall in Yokosuka on Monday and asked that a backpack with a letter inside be given to the mayor, the official who met him told AFP.

"We found 60 million yen ($550,850) in cash inside and a letter saying 'This is the money I've been saving since the first grade. Please make use of it. It's a donation,'" said the official.

The man appeared to be in his 70s or 80s and declined to give his name, saying he wanted to stay anonymous.

"We've never received such a big donation from an anonymous person," the official added.

Mayor Katsuaki Kamiji said in a statement he was "surprised and moved" by the donation, particularly during the hardship of the pandemic.

"I'm speechless and full of gratitude," he said.

Japan is no stranger to anonymous donors.

Last year, a man appeared at the Nara city hall with a bag filled with 30 million yen in cash. He left a note inside saying he wanted the money to be used to help the poor and fund education, according to local media.

And elsewhere last year, a hospital in Kobe received five million yen in cash sent by mail by an anonymous donor.