A hackers group which calls itself Lizard Squad claims to have paralysed gaming networks Microsoft's Xbox Live and Google's PlayStation on Christmas Day.
Thousands of gamers have reported widespread disruption on the day with many disappointed as they could not try out their Christmas presents.
"We're aware that some of you are experiencing trouble signing in to Xbox Live, and we want you to know we're working to address this as quickly as we possibly can. Thanks for your patience! We'll update you on our progress in a half hour," Xbox Live said in a statement.
The gaming networks, which allow users to play video games with the online community, first experienced attacks on Wednesday, 24 December, which went on into Christmas Day.
The Lizard Squad, a relatively-unknown clan of hackers, claimed the distributed denial of service (DDOS) attacks and wrote on Twitter: "Jingle bells jingle bells Xbox got ran. oh my fun it is to troll of you morons ... hey!"
The following message on Twitter demanded 100,000 retweets on the micro-blogging site for the gaming networks to be reinstated. It read: "Get me to 100k or Xbox Live will remain #offline RT!"
The official PlayStation support account on Twitter acknowledged there were glitches but did not identify the cause.
The network owned by Sony, which was also the target of a cyber attack over the North Korean movie The Interview,said: "We are aware that some users are reporting issues accessing PSN this morning. Thanks for your patience as we investigate."