Sony today apologised for a security breach that compromised millions of users, and said that while it had no evidence that credit card information was stolen it could not rule it out.

Sony executives bowed in apology and said the company would begin restoring its PlayStation Network and Qriocity online services in the next week and improve security measures after the breach that hit 77 million accounts.

"This criminal act against our network had a significant impact not only on our consumers, but our entire industry," said Sony executive deputy president Kazuo Hirai.

"These illegal attacks obviously highlight the widespread problem with cyber security. We take the security of our consumers' information very seriously and are committed to helping our consumers protect their personal data."

The electronics giant held an unusual Sunday news conference on the breach, which was feared to have involved the theft of details on 10 million registered credit cards and which the company has said was carried out by hackers.

The PlayStation Network and Qriocity streaming music service were shut down on April 20 after what Sony described as an "external intrusion" and remain offline as the company upgrades security and works with US federal investigators.

The United States, Britain, Australia and Hong Kong are investigating the hacking and theft of personal data which included names, gender, addresses, email addresses, birthdays and login passwords for the PlayStation network and Qriocity networks.

A US House of Representatives panel Friday sent a letter to Hirai with questions on the data breach.

It also asked Sony to explain why it believes credit card information was not taken despite being unable to determine the exact scale of the theft.

"We do not have clear evidence but we also cannot rule out the possibility of credit card data theft," Hirai told reporters today. "We have to regain the trust and confidence of our users."

By way of compensation, Sony said it would offer customers free downloads, services and 30 days free premium membership periods for eligible customers.

Sony said it had worked with security firms and "implemented significant security measures to further detect unauthorised activity and provide consumers with greater protection of their personal information" and would create a new security officer position.

It said it would add automated monitoring to help defend against any new attacks, and offer enhanced levels of data protection and encryption, and additional firewalls.

Sony is being sued in a US court by gamers who have accused the company of being negligent and breaching its contracts with PlayStation Network users.