Several popular social networking sites including Facebook and Instagram suffered widespread outages Tuesday before coming back online several hours later.

No official reason for the disruption was given, but a hacker group that calls itself Lizard Squad claimed responsibility for the blackout in a Twitter post.

Image-sharing social network Instagram posted on Twitter on Tuesday that it was aware of the problem and was "working on a fix."

Lizard Squad, also on Twitter, warned there was "more to come" and that the group was "organizing the [Malaysia Airlines] email dump."

The message referred to Malaysia Airlines' website, which was blocked by hackers on Monday.

The site MalaysiaAirlines.com showed messages saying, "Lizard Squad Will Prevail" and "404-Plane Not Found," and a picture of a lizard in a tuxedo with a pipe in its mouth.

They posted a photo with caption: "Hacked by Lizard Squad: Official Cyber Caliphate."

The Lizard Squad group in December claimed to crash the online services of gaming consoles Xbox and PlayStation the day after Christmas.

There are more than 1.35 billion active users on Facebook. Instagram has more than 100 million active users since the company launched in 2010.