It's rare for Facebook Chief Executive Officer Mark Zuckerberg to interact publicly with other moguls online. When he does, it's usually friendly and choreographed, like the time he asked Microsoft founder and fellow billionaire Bill Gates for help on a Harvard University commencement speech.

But with Elon Musk, the CEO of Tesla and Space Exploration Technologies, it hasn't been as cordial. In a live video Q&A on Facebook on Monday, Zuckerberg was asked what he thought about Musk's calls for proactive regulation of artificial intelligence, before the robots become dangerously smarter than their creators and pose an existential threat to humanity.

"People who are naysayers and try to drum up these doomsday scenarios, I just, I don't understand it," Zuckerberg said in the video. "It's really negative and in some ways I actually think it is pretty irresponsible."

Zuckerberg said he was optimistic about the technology, and that people shouldn't call for a slowdown in progress with artificial intelligence.

Musk shot back on Twitter.

It's not the first time the two have clashed publicly. Last year, a SpaceX rocket exploded on a launchpad in Florida. The rocket was carrying a satellite that was supposed to help Facebook spread internet connectivity in Africa.

Zuckerberg, who was travelling in Africa at the time, wrote on Facebook that he was "deeply disappointed to hear that SpaceX's launch failure destroyed our satellite."

The term artificial intelligence, or AI, is used to describe machines with computer code that learns as it goes. The technology is becoming widely used in sectors such as healthcare, entertainment and banking.

Fear that machines could become so intelligent that they might rise up and overthrow humanity is a common theme in science fiction.

Musk told a gathering of US governors this month that the potential dangers are not so imaginary, and that they should move to regulate AI.

"I keep sounding the alarm bell, but until people see robots going down the street killing people, they don't know how to react, because it seems so ethereal," Musk said, according to a video of the event.

"AI is a fundamental risk to the existence of human civilisation," he added.

Zuckerberg, who was grilling brisket at home while answering viewers' questions during the live video Q&A, said AI could result in better diagnoses of diseases and the elimination of car wrecks, and he said he did not see how "in good conscience" people could want to slow down the development of AI through regulation. 

Bloomberg/Reuters