"We have seen recently the emergence of political populism, which sometimes has a major impact on political systems" in Europe and elsewhere, Antonio Guterres said.
"Such phenomena have a negative impact on public opinion and trigger hostile reactions toward foreigners, xenophobia and racism, which hampers the protection of refugees."
The former Portuguese prime minister said the trend "creates an environment favorable to violent and barbarous acts such as that in Norway," where a 32-year-old right-wing extremist killed 77 people on July 22.
Guterres expressed concern about this political populism at a time when the world is dealing with a massive refugee crisis.
In recent months, successive crises have unfolded in Ivory Coast, Libya, Syria, Yemen, Sudan and the Horn of Africa, with hundreds of thousands of refugees displaced