Global banking group HSBC has admitted to losing a computer server with the transaction data of 159,000 account holders in Hong Kong branch, sparking anger among some customers who closed accounts.

The bank said it had lost track of the server during renovation work at a Kwun Tong district branch in east Kowloon on April 26. Police say the server was stolen and they are still investigating the case.

The data on the server includes account numbers, customer names, transaction amounts and transaction types, but does not contain any customer PINS, passwords or user IDs, the company said in a statement.

"The server is protected by multiple layers of security. The risk of data leakage and fraudulent transactions resulting from the loss of the server is deemed to be low," it added.

The chairman of HSBC's China and Asia Operations, Vincent Cheng, apologised to affected customers, and said none of them would be liable for any financial losses which might arise from fraudulent activities.

"On behalf of HSBC, I apologise to all affected customers. We (HSBC) are also victims of this loss, but of course we will bear the responsibility," Cheng told reporters.

Despite this, some affected customers expressed anger at the data breach, with local television showing customers flocking to the branch on Thursday and in some cases closing accounts.

"I'm worried, other people now know my ID (identity) card number and how much money I have. It's a big deal," one lady told Hong Kong's Cable Television.

Others criticised the bank for taking nearly two weeks to confirm the data theft and inform customers.

But HSBC said it had followed established procedures and needed time to carry out its own internal investigations.

 "We reported on this case within five working days to the Hong Kong Monetary Authority, but we also have to review whether we did the best we could during this process," said HSBC's Cheng. - Reuters