The National Police Agency said Friday that it suspects several groups were involved in printing the counterfeit 10,000 yen bills discovered in several prefectures during the New Year's period.
An analysis of some 340 bills from 12 prefectures found eight different serial numbers used on the counterfeit bank notes.
The NPA said it will hold a nationwide meeting of police officers Tuesday to fight the counterfeiting.
At least 820 fake 10,000 yen bills, which were apparently color-copied, were used during the yearend and New Year's period at shops, mainly around shrines and temples across the nation, according to a Kyodo News tally as of Thursday.
Police in Nara Prefecture said the same day that a 45-year-old man arrested earlier in the week for allegedly using forged currency was found to have visited Kyoto's Fushimi Inari Taisha Shrine and Sumiyoshi Taisha Shrine in Osaka during the holidays.
Digital images of one type of the fake bills were found during a search of his home. Bogus notes were also found in the vicinity of both shrines.