Musk posted a comment on the futurology site Edge.org, warning readers that developments in AI could bring about robots that may autonomously decide that it is sensible to start killing humans.
"The risk of something seriously dangerous happening is in the five year timeframe," Musk wrote.
Aware that internet commenters may mock him for his outlandish predictions, Musk defended his views, writing, "This is not a case of crying wolf about something I don't understand."
But minutes after he posted the comment, it was deleted.
The billionaire entrepreneur has made a habit of making apocalyptic comments about killer robots in recent interviews.
During a talk at a recent Vanity Fair conference, Musk warned the audience about killer robots. He suggested that advanced artificial intelligence could cause robots to delete humans like spam:
If its [function] is just something like getting rid of e-mail spam and it determines the best way of getting rid of spam is getting rid of humans ...