United Nations Secretary-General Antonio Guterres speaks at a press conference during the COP29 UN climate change conference in Baku, Azerbaijan Nov. 21. Reuters-Yonhap

Uncontrolled social media networks and artificial intelligence amplify the worst human impulses, allowing hate speech to spread like wildfire and ignite violence, UN secretary general Antonio Guterres said on Tuesday.

"We must reign in hate speech and disinformation spreading online," Guterres told a top-level meeting of the United Nations' Alliance of Civilisations (UNAOC) in Portugal.

"Unchecked digital platforms and Artificial Intelligence have endowed hate speech with a speed and reach unseen before," he told UNAOC's 10th global forum in Cascais, near Lisbon.

"The worst impulses of humanity are given a megaphone, and many times they lead to violence," he told a session at the gathering on "upending hate".

The proliferation of deepfakes online allowed "the impossible and the unverified (to) become credible in an instant", Guterres said.

"Misinformation and outright lies are fuelling repulsive anti-semitism, anti-Muslim bigotry and attacks on minority Christian communities, among others," Guterres said.

Social media and AI offered a "new medium" for these "old tactics".

The UN leader reiterated his pleas for peace in Gaza, Lebanon, Ukraine and Sudan.

The UN Alliance of Civilisations seeks to promote "cultural diversity, religious pluralism and mutual respect".

This year's global forum -- whose attendees include presidents, ministers and the heads of international bodies -- runs from November 25 to 27. (AFP)