United Nations chief Antonio Guterres warned on Tuesday against "dangerous rhetoric" stoking tensions among nuclear-armed rivals.
"Growing divisions are threatening global peace and security, provoking new confrontations and making it all the more difficult to resolve old conflicts," Guterres told a conference in Morocco.
"Dangerous rhetoric is raising nuclear tensions," he warned.
"At the same time, we are dangerously close to the edge on the climate, while hate speech and disinformation are proliferating."
He was talking as Russia's war in Ukraine neared its tenth month with no end in sight, fanning nuclear fears.
Guterres said "forces of discord" were waking up "old demons" including anti-semitism and Islamophobia.
"In this troubled world, we must ease tensions, foster inclusion and social cohesion, and bring about more united and resilient societies," he said.
Guterres was addressing a meeting of the United Nations Alliance of Civilizations, which aims to "galvanise international action against extremism" -- the first time the group has met on African soil.
In a declaration adopted on Tuesday evening, the meeting condemned "any advocacy of hatred that constitutes incitement to discrimination, hostility or violence".
It also expressed "deep concern about the use of new information technologies... for purposes contrary to respect for human values, good neighbourliness, equality, non-discrimination, and respect for others", noting the particular vulnerability of children and youth.
The Fez meeting ends Wednesday. The forum's next edition is to be held in Lisbon in 2024.