Technical difficulties first arose on Thursday evening and continued into Friday. Both companies have been posting on Twitter and their websites to keep customers informed of the work being done to restore the online service.

Sony's PlayStation Twitter account said on Friday: "We're aware that some users are having issues logging into PSN - engineers are investigating."

Meanwhile the Microsoft website for Xbox users said: "We're aware of this issue, and we're working to find a fix ASAP! We appreciate your patience in the meantime, and we encourage you to retry signing in when you get a chance. We'll update you as soon as we know more."

A new Twitter account, using the same name of a group of hackers which has targeted Sony in the past, has claimed responsibility for bringing down the consoles' online services. The authenticity of the Twitter account, which has only been active since Wednesday, remains unverified.

Since Christmas Eve, the "Lizard Squad" account has been taunting other users, demanding, in numerous posts, a certain number of retweets in order for Xbox or PlayStation to be put back online.

Connections to the Sony cyberattack earlier this month have already been drawn, but could not be confirmed.

Sony Pictures became the victim of a sophisticated hacking attack in which massive amounts of data from its servers were stolen and subsequently released.

The US has blamed North Korea for the attack, claiming that it was in response to Sony's satirical comedy "The Interview," which depicts a plot to kill North Korean dictator Kim Jong Un.

After initially canceling the December 25 release of "The Interview," Sony backtracked, bringing it out in some 300 US cinemas and making it available online - including through the Xbox console and, soon, the PlayStation.

The latter was also hit by a huge cyberattack in 2011. Personal details from 77 million customers were stolen, preventing them from playing online and forcing Sony to disable the network for more than three weeks.

ksb/tj (Reuters, AFP)