Tesla and SpaceX CEO Elon Musk Tuesday tweeted that Facebook founder Mark Zuckerberg's knowledge of the artificial intelligence (AI) is limited. The two tech giants have been locked in a public feud over AI.

"His (Mark Zuckerberg's) understanding of the subject is limited," Musk wrote on his twitter Monday after Zuckerberg blasted his warning against AI.

Musk has repeatedly expressed his concern about the potential danger of AI, regarding the technology as a threat to the human race in the future.

On July 15, when Musk attended the National Governors Association 2017 Summer Meeting held in the U.S. state of Rhode Island, he stressed AI may pose a "fundamental risk to the existence of civilization" and called again for proactive regulation of the controversial technology by the government.

However, Zuckerberg has a different view on this issue.

On Monday, while taking questions during a Facebook Live broadcast, Zuckerberg was asked for his thoughts on AI and its possible influence as a response to Elon Musk's comments.

"I have pretty strong opinions on this. I am optimistic. And I think people who are naysayers and try to drum up these doomsday scenarios -- I just, I don't understand it. It's really negative and in some ways I actually think it is pretty irresponsible," he said.

In the broadcast, Zuckerberg also said AI will have many realistic applications, like saving lives through disease diagnosis and powering driverless cars, which can create dramatic improvement for human society.