Facebook and Instagram offline

Social media websites Facebook and Instagram are back online after an apparent worldwide shutdown.

The online blackout lasted more than half an hour on Tuesday.

Matchmaking mobile app Tinder also went down.

It is not clear what caused the outages.

Instagram had tweeted it was trying to fix the problem but deleted the post once the issue was resolved.

"We're aware of an outage affecting Instagram and are working on a fix. Thank you for your patience," it said.

People took to Twitter to express their frustration and eventual relief over the blackout, using the hashtags #facebookdown and #instagramdown.

Hacking group Lizard Squad has claimed responsibility for the shutdown.

"Facebook, Instagram, Tinder, AIM, Hipchat #offline #LizardSquad," it tweeted.

Lizard Squad recently claimed responsibility for hacking the Malaysia Airlines website, in which it displayed a picture a lizard wearing a top hat over the error message "404 - Plane Not Found".