Impunity in the face of repeated attacks on religious leaders and places of worship, combined with weak prevention and poor accountability, is leading victims in Nigeria to view violence as persecution or even genocide, according to a United Nations report.

Spreading violence and impunity for armed groups is undermining religious freedom in Nigeria, the UN's top expert on the matter said Friday, adding it was understandable that some victims "describe this as persecution or genocide".

The comments by the United Nations special rapporteur on religious freedom, Nazila Ghanea, came after US President Donald Trump angered Nigeria last year by condemning what he called a Christian "genocide" in the country.

Nigeria, which is divided between a mostly Muslim north and Christian-majority south, is struggling to deal with multiple security crises, including a long-running jihadist insurgency and so-called "bandit" gangs in the north, as well as farmer-herder conflicts in the religiously mixed centre.

The US and European religious right have pushed accusations that the persecution of Christians is driving violence in Africa's most populous country.