A hacker has gained access to one of Vodafone Germany's servers and has stolen the personal data of about 2 million customers, the company said on Thursday.

The hacker had access to customers' names, addresses and bank account numbers, the group said, adding the person did not get any passwords, security numbers or connection data.

Vodafone said it was not possible that the data was of any use to the hacker. "It is hardly possible to use the data to get directly access to the bank accounts of those affected," Vodafone said in a statement.

Privacy and personal data are sensitive issues in Germany due partly to a history of heavy surveillance of citizens in the former communist East and under Hitler's Nazis.

Vodafone warned its customers that with potential so-called "phishing" attacks or fake e-mails criminals would try to get more information about passwords and credit cards.

It said it was working with police to investigate the matter and had sealed the ports the hacker had used to get access to its servers.