The emergence of artificial intelligence (AI) could be the "worst event in the history of our civilization" unless society finds a way to control its development, high-profile physicist Stephen Hawking said Monday.

He made the comments during a talk at the Web Summit technology conference in Lisbon, Portugal, in which he said, "computers can, in theory, emulate human intelligence, and exceed it."

Hawking talked up the potential of AI to help undo damage done to the natural world, or eradicate poverty and disease, with every aspect of society being "transformed."

But he admitted the future was uncertain.

"Success in creating effective AI, could be the biggest event in the history of our civilization. Or the worst. We just don't know. So we cannot know if we will be infinitely helped by AI, or ignored by it and side-lined, or conceivably destroyed by it," Hawking said during the speech.

"Unless we learn how to prepare for, and avoid, the potential risks, AI could be the worst event in the history of our civilization. It brings dangers, like powerful autonomous weapons, or new ways for the few to oppress the many. It could bring great disruption to our economy."