Japan's financial watchdog said it requested Mizuho Financial Group Inc. and its banking arm Mizuho Bank to submit a work plan for system maintenance after a series of system failures this year, in a rare move to effectively oversee the system of a major bank, Kyodo News reported. The Financial Services Agency made the request as part of its business improvement order issued amid lingering concerns over the security of the financial group's system after it experienced seven failures this year. Mizuho, one of the three Japanese megabanks, is still working to identify the root causes of the series of failures including the latest system problem that disrupted about 100 automated teller machines on Sept. 8. The latest order comes after Mizuho reported details of the first five failures and measures to prevent recurrences to the FSA on two occasions earlier this year as requested. Of the five cases, the first four occurred within two weeks after Feb. 28, when over 4,300, or about 80 percent of Mizuho's ATMs operating nationwide, were temporarily suspended and more than 5,000 bank cards and books were stuck inside them. A panel of lawyers and computer system experts set up by the bank concluded in June that the four system problems were caused by poor operation and management rather than system defects. Read more.