Mizuho Bank experienced a system failure Wednesday that disrupted the operations of about 100 ATMs, the major Japanese banking group said, marking the seventh such outage this year.

The failure occurred around 9:20 a.m. due to a "hardware problem," but affected services have been restored, the bank said.

The last system problem, on Aug. 23, disrupted around 130 ATMs, which followed a more extensive disruption, on Aug. 20, that had affected transactions at branch counters across Japan. Mizuho Bank is the core unit of Mizuho Financial Group Inc.

The bank also saw large-scale system failures in April 2002 and March 2011.