Sony Computer Entertainment in Tokyo said Monday the problem lasted two hours but has been fixed globally. It said the cause is under investigation, but there is no sign of any material being stolen.
The Japanese giant acknowledged the problem on Twitter on Sunday, saying, " We are aware that users are having issues connecting to PSN. Thanks for your patience as we investigate."
An hour early, a notorious hacking group called the Lizard Squad, took credit for the hack on Twitter, saying, "PSN Login #offline #LizardSquad".
Last week, the computer systems of Sony Pictures Entertainment were disrupted by a cyber-attack and confidential information including unreleased movies was leaked on the Internet.
North Korea was among the suspects, but it has denied responsibility.
The FBI is investigating threatening emails sent to some employees of Sony Pictures Entertainment, and trying to identify the person or group responsible.
There was no indication of a link between the PlayStation and Sony Pictures incidents.
Written with inputs from AP
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