Of the debit cards possibly affected, 600,000 are on the RuPay platform, NPCI said.

Highlights Security of 3.2 million cards may have been compromised, NPCI said

Out of this 0.6 million are RuPay cards

SBI said it has blocked over 6 lakh cards

About 3.2 million cards used at ATMs may have been compromised by a massive security breach, the National Payments Corporation of India or NPCI has said."Necessary corrective actions already have been taken and hence there is no reason for bank customers to panic," said NPCI's managing director AP Hota.The government agency said it came to know of a potential data breach when it had received complaints from banks that some customers' cards were used fraudulently in China and USA, while the owners were in India.It has received complaints of fraud transactions of a total 1.3 crore from 641 customers, who hold cards of 19 banks.The country's biggest lender State Bank of India has said it has blocked and will replace 6,25,000 debit cards as precaution and that its customers will be compensated for losses, which it estimates at about Rs 10 lakh to Rs 12 lakh."There is a suspicion that a data breach might have happened. We got this information from Visa, MasterCard and RuPay. As a measure of precaution, we have decided to replace these cards, which have been blocked," SBI managing director Rajnish Kumar told NDTV.Mr Kumar said the concern was that if hackers have access to card numbers and passwords it could be misused for e-commerce transactions or fund transfers. New cards would reach SBI customers soon, he said.The banker said the suspected breach had happened outside his bank's ATM network.An ICICI Bank spokesperson confirmed that a "possible breach of information of debit cards has taken place in the ATM network of another bank". As a precautionary measure, the PINs of debit cards used at the ATMs of that bank had been changed to protect customers, the bank said.Rajiv Anand, executive director of Axis Bank, too told NDTV that there had been no data breach at his bank's ATM network. "We have sent SMSes to customers to change PINs who were potentially exposed to a possible breach in other bank's network." he said.Where customers had not reset their PINs, cards had been blocked, Mr Anand said.He said "some sort of malware was sitting in one of the bank's network. As a result, banks found that customers came to them saying that they were hit by transactions they had not done."

YES Bank said in a statement that it has proactively undertaken a review of its ATMs and found no evidence of any breach. The bank said it continues to work with other banks and the NPCI to ensure safety and security of its ATM network and payment services.There were 697.2 million debit cards in India as of end-July, according to data from the Reserve Bank of India.