Sony has restored service for the PS4 game console on its PlayStation Network, three days after the online gaming operation and Microsoft's Xbox Live has been hit by connection failures on Christmas Day. Service was restored for Microsoft the next day, and the PlayStation Network briefly returned online for the PS3 and PS Vita game consoles on Saturday. Sony said some users were experiencing difficulty logging into the network. Hackers calling themselves Lizard Squad claimed responsibility for the network disruptions. The game networks were attacked on the same day Sony released The Interview online and in independent theatres, after major US cinema chains decided not to show the movie following hacking incidents at the company's film and TV studio last month. A different group called Guardians of Peace claimed responsibility for infiltrating Sony Pictures Entertainment's servers, destroying data, exposing Hollywood secrets and forcing the studio temporarily to cancel the film's release. "It's not yet clear whether it's just an outage of the PlayStation Network or if some personal data has been stolen too," Hideki Yasuda, a Tokyo-based analyst at Ace Research Institute, said. Lizard Squad, which took credit for an attack on Sony earlier this year, said on its Twitter account that it was behind the incidents. Cybercriminals targeted Sony in 2011 after it sued a young researcher when he exposed security vulnerabilities in the popular PlayStation 3 console. The 2011 hack involved the theft of personal data on 77 million PSN users.