"Needless to say this is not the experience we would like our customers to have and we sincerely regret the inconvenience," said another tweet.
Customers have faced issues while transacting and using the site and the mobile app since Monday and have vented their anguish on social media.
One Chandrakant Kumar tweeted "More HDFC netbanking getting worst for a couple of days. Unable to do anything online. Fund transfer also not working."
Another person with the tweeter handle @abhiman55197755 wrote "More I am still facing same problem with net banking please fix it #hdfcbankdown #hdfc bank care."