HK cardholders have reported odd transactions after last week's hacking A total of 12,000 credit cards will have to be replaced as a result of the world's biggest privacy violations that put as many as 40 million accounts worldwide at risk of fraud, a Hong Kong Monetary Authority executive said. Director of banking supervision Arthur Yuen Kwok-hang said most lenders had been able to contact the affected customers and had arranged for replacement cards. Banks would keep trying to contact the remaining customers, he said. '[The 12,000 cards] is a pretty big number but if you compare that to the total number of cards in circulation in Hong Kong then the problem isn't that severe,' Mr Yuen said. Authority chief executive Joseph Yam Chi-kwong on Tuesday said as many as 20,000 out of the 9.39 million credit cards in circulation in Hong Kong could be affected. Mr Yuen revealed that banks had received cardholders' reports of suspicious transactions, though he declined to provide exact figures. He said the priority of banks would be to identify cardholders who had been affected and to arrange for replacement cards to be issued. Mr Yuen estimated that most banks would complete the process within two weeks. DBS Bank managing director and head of consumer banking Sunny Cheung Yiu-tong said its replacement process was going smoothly. 'We have immediately blocked all accounts that were confirmed to be affected,' said Mr Cheung, revealing that the bank has a few hundred affected accounts. 'So far we haven't heard any complaints from customers and there were no reported losses.' Even cardholders not on the list of affected accounts had asked to have their cards replaced as a precaution, he said. 'Some customers have gone to the US during the affected period and they are pretty worried,' Mr Cheung said. 'So we replaced their cards as well even if they are not on the so-called hit list.' Mr Cheung said he did not see the need to use extra security measures on credit cards in the short term, but the bank had been trying to improve customers' knowledge on how to detect credit card fraud. The worldwide fraud emerged last week when credit card processing company CardSystems Solutions in the United States revealed that hackers had accessed its database.