Japanese banks that lost some 1.8 billion yen ($16.5 million) when fake overseas cards were used at convenience store ATMs are scrambling to combat such fraud.

Two banks that operate ATMs in convenience stores say they have reduced the withdrawal limit for customers using non-Japanese cards.

Japanese media have reported that the illegal withdrawals took place on May 15. The thefts occurred in 17 prefectures (states).

The reports say fake cards of a South African bank were used, and police have arrested three suspects so far.

Seven Bank spokesman Masatoshi Ogihara said the bank is also strengthening monitoring and cooperation with police but declined to provide specifics.