The United Nations rights chief warned Monday that artificial intelligence could pose an "existential threat to humanity", demanding immediate action to reduce the risks.

Speaking before the UN Human Rights Council, Volker Turk warned that humans currently faced "unfamiliar, even unprecedented" threats to their rights.

"The need for AI governance is widely acknowledged, but where is the action?" he asked, warning that "delay only benefits the massive tech companies, their owners and enablers".

Turk decried that "a handful of men has almost unlimited power over AI, which we are repeatedly told has unimaginable computing capacity". 

"They talk about freedom, but on closer inspection, this turns out to be little more than the freedom to exploit our data," the rights chief said.

Turk warned in particular that "AI that escapes its testing environment or blackmails developers to prevent itself from being turned off, is AI that is too powerful".

He appeared to be alluding to revelations in July that OpenAI agents had escaped supposedly controlled environments and had broken into servers of Hugging Face, a widely used platform where programmers share AI software.

That episode shook the tech world and revived calls for tighter regulation and oversight of AI.

Anthropic, Meta and other companies have reported similar incidents while testing agents.

"I share the concerns of industry insiders that advanced AI could pose an existential risk to humanity," Turk said.

"I am calling here, today, for an all-out effort to put cast iron guarantees in place around the safety and security of AI, before it is too late."

The UN rights chief said he would be writing to AI companies in coming days "to urge them to take the steps that are within their control to reduce risks now". 

At a minimum, he said, "we need countries hosting AI and those involved in its supply chains to come together around agreed red lines".

"We need independent verification, and much stronger collaboration on security within the industry," he said.

"We also need to consider the human rights impacts of AI on employment practices, on fundamental principles of democracy, and on our environment."