The systems trouble lasted from 9:55 a.m to 10:05 a.m. (0055 to 0115 GMT), a bank spokesman said, adding that the problem was caused by an application failure, which has left the bank investigating how many ATMs are still not working, he said.

The affected cash dispensing machines, mainly located in Tokyo, the capital, and the Osaka region, swallowed 91 cash cards and bank books, some of which were not returned to customers, the spokesman added.

An ATM outage is particularly painful in cash-loving Japan, where electronic money has only recently made inroads.

Smaller rival Mizuho Financial Group Inc has set up a third-party panel to investigate similar large-scale system failures it experienced this year.

(Reporting by Takashi Umekawa; Editing by Clarence Fernandez)