Amazon has suffered a major data breach that caused customer names and email addresses to be disclosed on its website, just two days ahead of Black Friday.

The e-commerce giant said it has emailed affected customers but refused to give any more details on how many people were affected or where they are based.

The firm said the issue was not a breach of its website or any of its systems, but a technical issue that inadvertently posted customer names and email addresses to its website.

In a short statement, Amazon said: “We have fixed the issue and informed customers who may have been impacted.”

Customers who received the email were told: “Our website inadvertently disclosed your email address or name and email address due to a technical error. The issue has been fixed. This is not a result of anything you have done, and there is no need for you to change your password or take any other action. The impacted customers have been contacted.”

It added: “Amazon takes all security-related matters very seriously and your account security is our top priority. We have policies and security measures in place to ensure that your personal information remains secure.”

UK data regulator the Information Commissioner’s Office, which Amazon must inform of any data breach as part of the general data protection regulation (GDPR) introduced this year, said it was following the situation.

The timing of the breach could not have been worse for Amazon. While Black Friday predominantly takes place in the US around the Thanksgiving holiday, hundreds of UK retailers now also take part on what has become a multi-billion pound shopping day.

Richard Walters, chief technical officer of cybersecurity firm CensorNet, said those affected should ignore Amazons’s advice and consider changing their passwords.

“If the reports are correct, the information leaked – names and email addresses – is less significant than some of these other breaches, which saw card details leaked,” he said. “However, it would be wrong to assume that this makes the breach inconsequential. Cyber-criminals can do a lot of damage with a large database of names and emails.

“A large majority of people still use predictable passwords, and thanks to previous high-profile breaches many people’s passwords are also readily available on the dark web. For cyber-criminals, it then just becomes an exercise in joining the dots.

“If you’ve been affected, make sure you change your passwords quickly.”