Facebook CEO Mark Zuckerberg has apologised for the disruption in the services of Facebook, Whatsapp and Instagram as a tsunami 10.7 million complaints battered the US tech giant. He also assured users that the services are returning online on Tuesday.

"Facebook, Instagram, WhatsApp and Messenger are coming back online now," Zuckerberg said in a Facebook post.

"Sorry for the disruption today — I know how much you rely on our services to stay connected with the people you care about," he said.

WhatsApp, too, posted aTwitter message saying:  "Apologies to everyone who hasn't been able to use WhatsApp today. We're starting to slowly and carefully get WhatsApp working again. Thank you so much for your patience. We will continue to keep you updated when we have more information to share."

Users started reporting that Instagram, WhatsApp and other services under the Facebook umbrella are now accessible after the massive outage on Monday.

Downdetector, a site that monitors outages across the internet, said in a post on Monday that the Facebook service collapse is the largest it has ever seen.

The US logged the largest number of reports for disrupted service of more than 1.7 million, followed by Germany at 1.3 million and the Netherlands at 9,15,000 reports.

Monday's outage has left several services under the Facebook corporate umbrella, including Instagram, WhatsApp and Messenger, inaccessible.